Distributions: align head members, smarter RandomSource setter

src/Numerics/Distributions/Bernoulli.cs

@@ -47,16 +47,10 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Bernoulli : IDiscreteDistribution
     {
-        /// <summary>
-        /// The probability of generating a one.
-        /// </summary>
-        double _p;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _p;
+
         /// <summary>
         /// Initializes a new instance of the Bernoulli class.
         /// </summary>
@@ -115,29 +109,21 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Gets or sets the probability of generating a one.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        public double P
+        public System.Random RandomSource
         {
-            get { return _p; }
+            get { return _random; }
-            set { SetParameters(value); }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
+        /// Gets or sets the probability of generating a one.
         /// </summary>
-        public System.Random RandomSource
+        public double P
         {
-            get { return _random; }
+            get { return _p; }
-            set
+            set { SetParameters(value); }
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
         }
 
         /// <summary>

src/Numerics/Distributions/Beta.cs

@@ -53,21 +53,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Beta : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Beta shape parameter a.
-        /// </summary>
-        double _shapeA;
 
-        /// <summary>
+        double _shapeA;
-        /// Beta shape parameter b.
-        /// </summary>
         double _shapeB;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the Beta class.
         /// </summary>
@@ -130,6 +120,15 @@ namespace MathNet.Numerics.Distributions
             _shapeB = b;
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the A shape parameter of the Beta distribution.
         /// </summary>
@@ -148,23 +147,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_shapeA, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the Beta distribution.
         /// </summary>

src/Numerics/Distributions/Binomial.cs

@@ -47,20 +47,17 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Binomial : IDiscreteDistribution
     {
+        System.Random _random;
+
         /// <summary>
-        /// Stores the normalized binomial probability.
+        /// Success probability in each trial.
         /// </summary>
         double _p;
 
         /// <summary>
         /// The number of trials.
         /// </summary>
-        int _n;
+        int _trials;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
 
         /// <summary>
         /// Initializes a new instance of the Binomial class.
@@ -95,7 +92,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>a string representation of the distribution.</returns>
         public override string ToString()
         {
-            return "Binomial(Success Probability = " + _p + ", Number of Trials = " + _n + ")";
+            return "Binomial(Success Probability = " + _p + ", Number of Trials = " + _trials + ")";
         }
 
         /// <summary>
@@ -124,7 +121,16 @@ namespace MathNet.Numerics.Distributions
             }
 
             _p = p;
-            _n = n;
+            _trials = n;
+        }
+
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -133,7 +139,7 @@ namespace MathNet.Numerics.Distributions
         public double P
         {
             get { return _p; }
-            set { SetParameters(value, _n); }
+            set { SetParameters(value, _trials); }
         }
 
         /// <summary>
@@ -141,33 +147,16 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public int N
         {
-            get { return _n; }
+            get { return _trials; }
             set { SetParameters(_p, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>
         public double Mean
         {
-            get { return _p*_n; }
+            get { return _p*_trials; }
         }
 
         /// <summary>
@@ -175,7 +164,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double StdDev
         {
-            get { return Math.Sqrt(_p*(1.0 - _p)*_n); }
+            get { return Math.Sqrt(_p*(1.0 - _p)*_trials); }
         }
 
         /// <summary>
@@ -183,7 +172,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double Variance
         {
-            get { return _p*(1.0 - _p)*_n; }
+            get { return _p*(1.0 - _p)*_trials; }
         }
 
         /// <summary>
@@ -199,7 +188,7 @@ namespace MathNet.Numerics.Distributions
                 }
 
                 var e = 0.0;
-                for (var i = 0; i <= _n; i++)
+                for (var i = 0; i <= _trials; i++)
                 {
                     var p = Probability(i);
                     e -= p*Math.Log(p);
@@ -214,7 +203,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double Skewness
         {
-            get { return (1.0 - (2.0*_p))/Math.Sqrt(_n*_p*(1.0 - _p)); }
+            get { return (1.0 - (2.0*_p))/Math.Sqrt(_trials*_p*(1.0 - _p)); }
         }
 
         /// <summary>
@@ -230,7 +219,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public int Maximum
         {
-            get { return _n; }
+            get { return _trials; }
         }
 
         /// <summary>
@@ -242,7 +231,7 @@ namespace MathNet.Numerics.Distributions
             {
                 if (_p == 1.0)
                 {
-                    return _n;
+                    return _trials;
                 }
 
                 if (_p == 0.0)
@@ -250,7 +239,7 @@ namespace MathNet.Numerics.Distributions
                     return 0;
                 }
 
-                return (int) Math.Floor((_n + 1)*_p);
+                return (int) Math.Floor((_trials + 1)*_p);
             }
         }
 
@@ -259,7 +248,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public int Median
         {
-            get { return (int) Math.Floor(_p*_n); }
+            get { return (int) Math.Floor(_p*_trials); }
         }
 
         /// <summary>
@@ -274,7 +263,7 @@ namespace MathNet.Numerics.Distributions
                 return 0.0;
             }
 
-            if (k > _n)
+            if (k > _trials)
             {
                 return 0.0;
             }
@@ -289,7 +278,7 @@ namespace MathNet.Numerics.Distributions
                 return 0.0;
             }
 
-            if (_p == 1.0 && k == _n)
+            if (_p == 1.0 && k == _trials)
             {
                 return 1.0;
             }
@@ -299,7 +288,7 @@ namespace MathNet.Numerics.Distributions
                 return 0.0;
             }
 
-            return SpecialFunctions.Binomial(_n, k)*Math.Pow(_p, k)*Math.Pow(1.0 - _p, _n - k);
+            return SpecialFunctions.Binomial(_trials, k)*Math.Pow(_p, k)*Math.Pow(1.0 - _p, _trials - k);
         }
 
         /// <summary>
@@ -314,7 +303,7 @@ namespace MathNet.Numerics.Distributions
                 return Double.NegativeInfinity;
             }
 
-            if (k > _n)
+            if (k > _trials)
             {
                 return Double.NegativeInfinity;
             }
@@ -329,7 +318,7 @@ namespace MathNet.Numerics.Distributions
                 return Double.NegativeInfinity;
             }
 
-            if (_p == 1.0 && k == _n)
+            if (_p == 1.0 && k == _trials)
             {
                 return 0.0;
             }
@@ -339,7 +328,7 @@ namespace MathNet.Numerics.Distributions
                 return Double.NegativeInfinity;
             }
 
-            return SpecialFunctions.BinomialLn(_n, k) + (k*Math.Log(_p)) + ((_n - k)*Math.Log(1.0 - _p));
+            return SpecialFunctions.BinomialLn(_trials, k) + (k*Math.Log(_p)) + ((_trials - k)*Math.Log(1.0 - _p));
         }
 
         /// <summary>
@@ -354,7 +343,7 @@ namespace MathNet.Numerics.Distributions
                 return 0.0;
             }
 
-            if (x > _n)
+            if (x > _trials)
             {
                 return 1.0;
             }
@@ -362,7 +351,7 @@ namespace MathNet.Numerics.Distributions
             var cdf = 0.0;
             for (var i = 0; i <= (int) Math.Floor(x); i++)
             {
-                cdf += Combinatorics.Combinations(_n, i)*Math.Pow(_p, i)*Math.Pow(1.0 - _p, _n - i);
+                cdf += Combinatorics.Combinations(_trials, i)*Math.Pow(_p, i)*Math.Pow(1.0 - _p, _trials - i);
             }
 
             return cdf;
@@ -392,7 +381,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>The number of successes in N trials.</returns>
         public int Sample()
         {
-            return SampleUnchecked(RandomSource, _p, _n);
+            return SampleUnchecked(RandomSource, _p, _trials);
         }
 
         /// <summary>
@@ -403,7 +392,7 @@ namespace MathNet.Numerics.Distributions
         {
             while (true)
             {
-                yield return SampleUnchecked(RandomSource, _p, _n);
+                yield return SampleUnchecked(RandomSource, _p, _trials);
             }
         }
 

src/Numerics/Distributions/Categorical.cs

@@ -53,6 +53,7 @@ namespace MathNet.Numerics.Distributions
     public class Categorical : IDiscreteDistribution
     {
         System.Random _random;
+
         double[] _pmfNormalized;
         double[] _cdfUnnormalized;
 
@@ -188,7 +189,15 @@ namespace MathNet.Numerics.Distributions
             {
                 _pmfNormalized[i] = p[i]/sum;
             }
+        }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -202,23 +211,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/Cauchy.cs

@@ -42,16 +42,10 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Cauchy : IContinuousDistribution
     {
-        /// <summary>
-        /// The scale of the Cauchy distribution.
-        /// </summary>
-        double _scale;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _scale;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Cauchy"/> class with the location parameter set to 0 and the scale parameter set to 1
         /// </summary>
@@ -84,6 +78,26 @@ namespace MathNet.Numerics.Distributions
             SetParameters(location, scale);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "Cauchy(Location = " + Median + ", Scale = " + _scale + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid. 
+        /// </summary>
+        /// <param name="location">Location parameter.</param>
+        /// <param name="scale">Scale parameter. Must be greater than 0.</param>
+        /// <returns>True when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double location, double scale)
+        {
+            return scale > 0.0 && !Double.IsNaN(location);
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -102,14 +116,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid. 
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="location">Location parameter.</param>
+        public System.Random RandomSource
-        /// <param name="scale">Scale parameter. Must be greater than 0.</param>
-        /// <returns>True when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double location, double scale)
         {
-            return scale > 0.0 && !Double.IsNaN(location);
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -130,31 +142,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(Median, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Cauchy(Location = " + Median + ", Scale = " + _scale + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
 
         /// <summary>
         /// Gets the mean of the distribution.

src/Numerics/Distributions/Chi.cs

@@ -48,16 +48,13 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Chi : IContinuousDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// Keeps track of the degrees of freedom for the Chi distribution.
         /// </summary>
         double _dof;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Chi"/> class. 
         /// </summary>
@@ -80,18 +77,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// A string representation of the distribution.
         /// </summary>
-        /// <param name="dof">The degrees of freedom for the Chi distribution.</param>
+        /// <returns>a string representation of the distribution.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        public override string ToString()
-        void SetParameters(double dof)
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(dof))
+            return "Chi(DoF = " + _dof + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _dof = dof;
         }
 
         /// <summary>
@@ -105,38 +96,36 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Gets or sets the degrees of freedom of the Chi distribution.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        public double DegreesOfFreedom
+        /// <param name="dof">The degrees of freedom for the Chi distribution.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double dof)
         {
-            get { return _dof; }
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(dof))
-            set { SetParameters(value); }
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            _dof = dof;
         }
 
         /// <summary>
-        /// A string representation of the distribution.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
+        public System.Random RandomSource
-        public override string ToString()
         {
-            return "Chi(DoF = " + _dof + ")";
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
-        /// Gets or sets the distribution's random number generator.
+        /// Gets or sets the degrees of freedom of the Chi distribution.
         /// </summary>
-        public System.Random RandomSource
+        public double DegreesOfFreedom
         {
-            get { return _random; }
+            get { return _dof; }
-            set
+            set { SetParameters(value); }
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
         }
 
         /// <summary>

src/Numerics/Distributions/ChiSquare.cs

@@ -46,9 +46,6 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class ChiSquare : IContinuousDistribution
     {
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
         /// <summary>
@@ -73,18 +70,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// A string representation of the distribution.
         /// </summary>
-        /// <param name="dof">The degrees of freedom for the <c>ChiSquare</c> distribution.</param>
+        /// <returns>a string representation of the distribution.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        public override string ToString()
-        void SetParameters(double dof)
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(dof))
+            return "ChiSquare(DoF = " + Mean + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            Mean = dof;
         }
 
         /// <summary>
@@ -98,38 +89,36 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Gets or sets the degrees of freedom of the <c>ChiSquare</c> distribution.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        public double DegreesOfFreedom
+        /// <param name="dof">The degrees of freedom for the <c>ChiSquare</c> distribution.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double dof)
         {
-            get { return Mean; }
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(dof))
-            set { SetParameters(value); }
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            Mean = dof;
         }
 
         /// <summary>
-        /// A string representation of the distribution.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
+        public System.Random RandomSource
-        public override string ToString()
         {
-            return "ChiSquare(DoF = " + Mean + ")";
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
-        /// Gets or sets the distribution's random number generator.
+        /// Gets or sets the degrees of freedom of the <c>ChiSquare</c> distribution.
         /// </summary>
-        public System.Random RandomSource
+        public double DegreesOfFreedom
         {
-            get { return _random; }
+            get { return Mean; }
-            set
+            set { SetParameters(value); }
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
         }
 
         /// <summary>

src/Numerics/Distributions/ContinuousUniform.cs

@@ -46,6 +46,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class ContinuousUniform : IContinuousDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The distribution's lower bound.
         /// </summary>
@@ -56,11 +58,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         double _upper;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the ContinuousUniform class with lower bound 0 and upper bound 1.
         /// </summary>
@@ -130,6 +127,15 @@ namespace MathNet.Numerics.Distributions
             _upper = upper;
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the lower bound of the distribution.
         /// </summary>
@@ -148,23 +154,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_lower, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/ConwayMaxwellPoisson.cs

@@ -53,6 +53,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class ConwayMaxwellPoisson : IDiscreteDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// Since many properties of the distribution can only be computed approximately, the tolerance
         /// level specifies how much error we accept.
@@ -84,11 +86,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         double _nu;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ConwayMaxwellPoisson"/> class. 
         /// </summary>
@@ -112,6 +109,28 @@ namespace MathNet.Numerics.Distributions
             SetParameters(lambda, nu);
         }
 
+        /// <summary>
+        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="System.String"/> that represents this instance.
+        /// </returns>
+        public override string ToString()
+        {
+            return "ConwayMaxwellPoisson(Lambda = " + _lambda + ", Nu = " + _nu + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid. 
+        /// </summary>
+        /// <param name="lambda">The lambda parameter.</param>
+        /// <param name="nu">The nu parameter.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double lambda, double nu)
+        {
+            return lambda > 0.0 && nu >= 0.0;
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -130,14 +149,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid. 
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="lambda">The lambda parameter.</param>
+        public System.Random RandomSource
-        /// <param name="nu">The nu parameter.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double lambda, double nu)
         {
-            return lambda > 0.0 && nu >= 0.0;
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -160,34 +177,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_lambda, value); }
         }
 
-        /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
-        /// </summary>
-        /// <returns>
-        /// A <see cref="System.String"/> that represents this instance.
-        /// </returns>
-        public override string ToString()
-        {
-            return "ConwayMaxwellPoisson(Lambda = " + _lambda + ", Nu = " + _nu + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/Dirichlet.cs

@@ -43,18 +43,15 @@ namespace MathNet.Numerics.Distributions
     /// <para>The statistics classes will check all the incoming parameters whether they are in the allowed
     /// range. This might involve heavy computation. Optionally, by setting Control.CheckDistributionParameters
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
-    public class Dirichlet
+    public class Dirichlet : IDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The Dirichlet distribution parameters.
         /// </summary>
         double[] _alpha;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the Dirichlet class. The distribution will
         /// be initialized with the default <seealso cref="System.Random"/> random number generator.
@@ -115,6 +112,17 @@ namespace MathNet.Numerics.Distributions
             SetParameters(parm);
         }
 
+        /// <summary>
+        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="System.String"/> that represents this instance.
+        /// </returns>
+        public override string ToString()
+        {
+            return "Dirichlet(Dimension = " + Dimension + ")";
+        }
+
         /// <summary>
         /// Checks whether the parameters of the distribution are valid: no
         /// parameter can be less than zero and at least one parameter should be
@@ -160,14 +168,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <returns>
+        public System.Random RandomSource
-        /// A <see cref="System.String"/> that represents this instance.
-        /// </returns>
-        public override string ToString()
         {
-            return "Dirichlet(Dimension = " + Dimension + ")";
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -308,23 +314,6 @@ namespace MathNet.Numerics.Distributions
             return term + SpecialFunctions.GammaLn(sumalpha);
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Samples a Dirichlet distributed random vector.
         /// </summary>

src/Numerics/Distributions/DiscreteUniform.cs

@@ -47,6 +47,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class DiscreteUniform : IDiscreteDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The distribution's lower bound.
         /// </summary>
@@ -57,11 +59,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         int _upper;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the DiscreteUniform class.
         /// </summary>
@@ -124,6 +121,15 @@ namespace MathNet.Numerics.Distributions
             _upper = upper;
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the lower bound of the probability distribution.
         /// </summary>
@@ -142,23 +148,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_lower, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/Erlang.cs

@@ -47,21 +47,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Erlang : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Erlang shape parameter.
-        /// </summary>
-        double _shape;
 
-        /// <summary>
+        double _shape;
-        /// Erlang inverse scale parameter.
-        /// </summary>
         double _invScale;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Erlang"/> class. 
         /// </summary>
@@ -109,6 +99,26 @@ namespace MathNet.Numerics.Distributions
             return new Erlang(shape, invScale);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "Erlang(Shape = " + _shape + ", Inverse Scale = " + _invScale + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid.
+        /// </summary>
+        /// <param name="shape">The shape of the Erlang distribution.</param>
+        /// <param name="invScale">The inverse scale of the Erlang distribution.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double shape, double invScale)
+        {
+            return shape >= 0.0 && invScale >= 0.0;
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -126,14 +136,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="shape">The shape of the Erlang distribution.</param>
+        public System.Random RandomSource
-        /// <param name="invScale">The inverse scale of the Erlang distribution.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double shape, double invScale)
         {
-            return shape >= 0.0 && invScale >= 0.0;
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -173,32 +181,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_shape, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Erlang(Shape = " + _shape + ", Inverse Scale = " + _invScale + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/Exponential.cs

@@ -46,16 +46,10 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Exponential : IContinuousDistribution
     {
-        /// <summary>
-        /// The lambda parameter of the Exponential distribution. 
-        /// </summary>
-        double _lambda;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _lambda;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Exponential"/> class.
         /// </summary>
@@ -78,18 +72,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// A string representation of the distribution.
         /// </summary>
-        /// <param name="lambda">Lambda parameter.</param>
+        /// <returns>a string representation of the distribution.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        public override string ToString()
-        void SetParameters(double lambda)
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(lambda))
+            return "Exponential(Lambda = " + _lambda + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _lambda = lambda;
         }
 
         /// <summary>
@@ -103,21 +91,18 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Gets or sets the lambda parameter of the distribution.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        public double Lambda
+        /// <param name="lambda">Lambda parameter.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double lambda)
         {
-            get { return _lambda; }
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(lambda))
-            set { SetParameters(value); }
+            {
-        }
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
 
-        /// <summary>
+            _lambda = lambda;
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Exponential(Lambda = " + _lambda + ")";
         }
 
         /// <summary>
@@ -126,15 +111,16 @@ namespace MathNet.Numerics.Distributions
         public System.Random RandomSource
         {
             get { return _random; }
-            set
+            set { _random = value ?? new System.Random(); }
-            {
+        }
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
 
-                _random = value;
+        /// <summary>
-            }
+        /// Gets or sets the lambda parameter of the distribution.
+        /// </summary>
+        public double Lambda
+        {
+            get { return _lambda; }
+            set { SetParameters(value); }
         }
 
         /// <summary>

src/Numerics/Distributions/FisherSnedecor.cs

@@ -46,6 +46,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class FisherSnedecor : IContinuousDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The first parameter - degree of freedom.
         /// </summary>
@@ -56,11 +58,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         double _d2;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="FisherSnedecor"/> class. 
         /// </summary>
@@ -84,6 +81,26 @@ namespace MathNet.Numerics.Distributions
             SetParameters(d1, d2);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "FisherSnedecor(DegreeOfFreedom1 = " + _d1 + ", DegreeOfFreedom2 = " + _d2 + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid.
+        /// </summary>
+        /// <param name="d1">The first parameter - degree of freedom.</param>
+        /// <param name="d2">The second parameter - degree of freedom.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double d1, double d2)
+        {
+            return d1 > 0.0 && d2 > 0.0;
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -101,14 +118,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="d1">The first parameter - degree of freedom.</param>
+        public System.Random RandomSource
-        /// <param name="d2">The second parameter - degree of freedom.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double d1, double d2)
         {
-            return d1 > 0.0 && d2 > 0.0;
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -129,32 +144,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_d1, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "FisherSnedecor(DegreeOfFreedom1 = " + _d1 + ", DegreeOfFreedom2 = " + _d2 + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the distribution's random number generator.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/Gamma.cs

@@ -54,21 +54,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Gamma : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Gamma shape parameter.
-        /// </summary>
-        double _shape;
 
-        /// <summary>
+        double _shape;
-        /// Gamma inverse scale parameter.
-        /// </summary>
         double _invScale;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the Gamma class.
         /// </summary>
@@ -153,6 +143,15 @@ namespace MathNet.Numerics.Distributions
             _invScale = invScale;
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the shape of the Gamma distribution.
         /// </summary>
@@ -190,23 +189,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_shape, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the Gamma distribution.
         /// </summary>

src/Numerics/Distributions/Geometric.cs

@@ -47,16 +47,10 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Geometric : IDiscreteDistribution
     {
-        /// <summary>
-        /// The geometric distribution parameter. 
-        /// </summary>
-        double _p;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _p;
+
         /// <summary>
         /// Initializes a new instance of the Geometric class.
         /// </summary>
@@ -81,18 +75,14 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// Returns a <see cref="System.String"/> that represents this instance.
         /// </summary>
-        /// <param name="p">The probability of generating a one.</param>
+        /// <returns>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        /// A <see cref="System.String"/> that represents this instance.
-        void SetParameters(double p)
+        /// </returns>
+        public override string ToString()
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(p))
+            return "Geometric(P = " + _p + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _p = p;
         }
 
         /// <summary>
@@ -106,41 +96,37 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Gets or sets the probability of generating a one.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        public double P
+        /// <param name="p">The probability of generating a one.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double p)
         {
-            get { return _p; }
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(p))
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
 
-            set { SetParameters(value); }
+            _p = p;
         }
 
         /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <returns>
+        public System.Random RandomSource
-        /// A <see cref="System.String"/> that represents this instance.
-        /// </returns>
-        public override string ToString()
         {
-            return "Geometric(P = " + _p + ")";
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
+        /// Gets or sets the probability of generating a one.
         /// </summary>
-        public System.Random RandomSource
+        public double P
         {
-            get { return _random; }
+            get { return _p; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
 
-                _random = value;
+            set { SetParameters(value); }
-            }
         }
 
         /// <summary>

src/Numerics/Distributions/Hypergeometric.cs

@@ -49,6 +49,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Hypergeometric : IDiscreteDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The size of the population (N).
         /// </summary>
@@ -64,11 +66,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         int _draws;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the Hypergeometric class.
         /// </summary>
@@ -94,6 +91,29 @@ namespace MathNet.Numerics.Distributions
             SetParameters(population, success, draws);
         }
 
+        /// <summary>
+        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// </summary>
+        /// <returns>
+        /// A <see cref="System.String"/> that represents this instance.
+        /// </returns>
+        public override string ToString()
+        {
+            return "Hypergeometric(N = " + _population + ", M = " + _success + ", n = " + _draws + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid.
+        /// </summary>
+        /// <param name="population">The size of the population (N).</param>
+        /// <param name="success">The number successes within the population (K, M).</param>
+        /// <param name="draws">The number of draws without replacement (n).</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(int population, int success, int draws)
+        {
+            return population >= 0 && success >= 0 && draws >= 0 && (success <= population && draws <= population);
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -113,15 +133,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="population">The size of the population (N).</param>
+        public System.Random RandomSource
-        /// <param name="success">The number successes within the population (K, M).</param>
-        /// <param name="draws">The number of draws without replacement (n).</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(int population, int success, int draws)
         {
-            return population >= 0 && success >= 0 && draws >= 0 && (success <= population && draws <= population);
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -181,34 +198,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_population, _success, value); }
         }
 
-        /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
-        /// </summary>
-        /// <returns>
-        /// A <see cref="System.String"/> that represents this instance.
-        /// </returns>
-        public override string ToString()
-        {
-            return "Hypergeometric(N = " + _population + ", M = " + _success + ", n = " + _draws + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/IDistribution.cs

@@ -0,0 +1,43 @@
+// <copyright file="IUnivariateDistribution.cs" company="Math.NET">
+// Math.NET Numerics, part of the Math.NET Project
+// http://numerics.mathdotnet.com
+// http://github.com/mathnet/mathnet-numerics
+// http://mathnetnumerics.codeplex.com
+//
+// Copyright (c) 2009-2013 Math.NET
+//
+// Permission is hereby granted, free of charge, to any person
+// obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without
+// restriction, including without limitation the rights to use,
+// copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+// OTHER DEALINGS IN THE SOFTWARE.
+// </copyright>
+
+namespace MathNet.Numerics.Distributions
+{
+    /// <summary>
+    /// The common interface for all distributions.
+    /// </summary>
+    public interface IDistribution
+    {
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        System.Random RandomSource { get; set; }
+    }
+}

src/Numerics/Distributions/IUnivariateDistribution.cs

@@ -30,18 +30,11 @@
 
 namespace MathNet.Numerics.Distributions
 {
-    using System;
-
     /// <summary>
     /// The interface for univariate distributions.
     /// </summary>
-    public interface IUnivariateDistribution
+    public interface IUnivariateDistribution : IDistribution
     {
-        /// <summary>
-        /// Gets or sets the random number generator which is used to generate random samples from the distribution.
-        /// </summary>
-        Random RandomSource { get; set; }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/InverseGamma.cs

@@ -47,21 +47,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class InverseGamma : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Inverse Gamma shape parameter. 
-        /// </summary>
-        double _shape;
 
-        /// <summary>
+        double _shape;
-        /// Inverse Gamma scale parameter scale. 
-        /// </summary>
         double _scale;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="InverseGamma"/> class. 
         /// </summary>
@@ -85,15 +75,31 @@ namespace MathNet.Numerics.Distributions
             SetParameters(shape, scale);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "InverseGamma(Shape = " + _shape + ", Inverse Scale = " + _scale + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid. 
+        /// </summary>
+        /// <param name="shape">The shape (alpha) parameter of the inverse Gamma distribution.</param>
+        /// <param name="scale">The scale (beta) parameter of the inverse Gamma distribution.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double shape, double scale)
+        {
+            return shape > 0.0 && scale > 0.0;
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        /// <param name="shape">
+        /// <param name="shape">The shape (alpha) parameter of the inverse Gamma distribution.</param>
-        /// The shape (alpha) parameter of the inverse Gamma distribution.
+        /// <param name="scale">The scale (beta) parameter of the inverse Gamma distribution.</param>
-        /// </param>
-        /// <param name="scale">
-        /// The scale (beta) parameter of the inverse Gamma distribution.
-        /// </param>
         /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
         void SetParameters(double shape, double scale)
         {
@@ -107,14 +113,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid. 
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="shape">The shape (alpha) parameter of the inverse Gamma distribution.</param>
+        public System.Random RandomSource
-        /// <param name="scale">The scale (beta) parameter of the inverse Gamma distribution.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double shape, double scale)
         {
-            return shape > 0.0 && scale > 0.0;
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -135,32 +139,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_shape, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "InverseGamma(Shape = " + _shape + ", Inverse Scale = " + _scale + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/InverseWishart.cs

@@ -46,8 +46,10 @@ namespace MathNet.Numerics.Distributions
     /// <para>The statistics classes will check all the incoming parameters whether they are in the allowed
     /// range. This might involve heavy computation. Optionally, by setting Control.CheckDistributionParameters
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
-    public class InverseWishart
+    public class InverseWishart : IDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The degrees of freedom for the inverse Wishart distribution.
         /// </summary>
@@ -63,11 +65,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         Cholesky<double> _chol;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="InverseWishart"/> class. 
         /// </summary>
@@ -100,24 +97,6 @@ namespace MathNet.Numerics.Distributions
             return "InverseWishart(Nu = " + _nu + ", Rows = " + _s.RowCount + ", Columns = " + _s.ColumnCount + ")";
         }
 
-        /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
-        /// </summary>
-        /// <param name="nu">The degrees of freedom for the Wishart distribution.</param>
-        /// <param name="s">The scale matrix for the Wishart distribution.</param>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
-        void SetParameters(double nu, Matrix<double> s)
-        {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(nu, s))
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _nu = nu;
-            _s = s;
-            _chol = Cholesky<double>.Create(_s);
-        }
-
         /// <summary>
         /// Checks whether the parameters of the distribution are valid. 
         /// </summary>
@@ -142,6 +121,33 @@ namespace MathNet.Numerics.Distributions
             return nu > 0.0;
         }
 
+        /// <summary>
+        /// Sets the parameters of the distribution after checking their validity.
+        /// </summary>
+        /// <param name="nu">The degrees of freedom for the Wishart distribution.</param>
+        /// <param name="s">The scale matrix for the Wishart distribution.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double nu, Matrix<double> s)
+        {
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(nu, s))
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            _nu = nu;
+            _s = s;
+            _chol = Cholesky<double>.Create(_s);
+        }
+
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the degrees of freedom for the inverse Wishart distribution.
         /// </summary>
@@ -160,23 +166,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_nu, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean.
         /// </summary>

src/Numerics/Distributions/Laplace.cs

@@ -48,16 +48,10 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Laplace : IContinuousDistribution
     {
-        /// <summary>
-        /// The scale of the Laplace distribution.
-        /// </summary>
-        double _scale;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _scale;
+
         /// <summary>
         /// Gets or sets the location of the Laplace distribution.
         /// </summary>
@@ -110,20 +104,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// A string representation of the distribution.
         /// </summary>
-        /// <param name="location">The location for the Laplace distribution.</param>
+        /// <returns>a string representation of the distribution.</returns>
-        /// <param name="scale">The scale for the Laplace distribution.</param>
+        public override string ToString()
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
-        void SetParameters(double location, double scale)
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(location, scale))
+            return "Laplace(Location = " + Mean + ", Scale = " + _scale + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            Mean = location;
-            _scale = scale;
         }
 
         /// <summary>
@@ -138,12 +124,20 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// A string representation of the distribution.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
+        /// <param name="location">The location for the Laplace distribution.</param>
-        public override string ToString()
+        /// <param name="scale">The scale for the Laplace distribution.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double location, double scale)
         {
-            return "Laplace(Location = " + Mean + ", Scale = " + _scale + ")";
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(location, scale))
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            Mean = location;
+            _scale = scale;
         }
 
         /// <summary>
@@ -152,15 +146,7 @@ namespace MathNet.Numerics.Distributions
         public System.Random RandomSource
         {
             get { return _random; }
-            set
+            set { _random = value ?? new System.Random(); }
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
         }
 
         /// <summary>

src/Numerics/Distributions/LogNormal.cs

@@ -48,21 +48,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class LogNormal : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Keeps track of the mu of the logarithm of the log-log-normal distribution.
-        /// </summary>
-        double _mu;
 
-        /// <summary>
+        double _mu;
-        /// Keeps track of the standard deviation of the logarithm of the log-log-normal distribution.
-        /// </summary>
         double _sigma;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="LogNormal"/> class. 
         /// The distribution will be initialized with the default <seealso cref="System.Random"/>
@@ -149,6 +139,15 @@ namespace MathNet.Numerics.Distributions
             _sigma = sigma;
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the mean of the logarithm of the log-normal.
         /// </summary>
@@ -167,23 +166,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_mu, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mu of the log-normal distribution.
         /// </summary>

src/Numerics/Distributions/MatrixNormal.cs

@@ -47,8 +47,10 @@ namespace MathNet.Numerics.Distributions
     /// <para>The statistics classes will check all the incoming parameters whether they are in the allowed
     /// range. This might involve heavy computation. Optionally, by setting Control.CheckDistributionParameters
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
-    public class MatrixNormal
+    public class MatrixNormal : IDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The mean of the matrix normal distribution.        
         /// </summary>
@@ -64,11 +66,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         Matrix<double> _k;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="MatrixNormal"/> class. 
         /// </summary>
@@ -107,55 +104,6 @@ namespace MathNet.Numerics.Distributions
             return "MatrixNormal(Rows = " + _m.RowCount + ", Columns = " + _m.ColumnCount + ")";
         }
 
-        /// <summary>
-        /// Gets or sets the mean. (M)
-        /// </summary>
-        /// <value>The mean of the distribution.</value>
-        public Matrix<double> Mean
-        {
-            get { return _m; }
-            set { SetParameters(value, _v, _k); }
-        }
-
-        /// <summary>
-        /// Gets or sets the row covariance. (V)
-        /// </summary>
-        /// <value>The row covariance.</value>
-        public Matrix<double> RowCovariance
-        {
-            get { return _v; }
-            set { SetParameters(_m, value, _k); }
-        }
-
-        /// <summary>
-        /// Gets or sets the column covariance. (K)
-        /// </summary>
-        /// <value>The column covariance.</value>
-        public Matrix<double> ColumnCovariance
-        {
-            get { return _k; }
-            set { SetParameters(_m, _v, value); }
-        }
-
-        /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
-        /// </summary>
-        /// <param name="m">The mean of the matrix normal.</param>
-        /// <param name="v">The covariance matrix for the rows.</param>
-        /// <param name="k">The covariance matrix for the columns.</param>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
-        void SetParameters(Matrix<double> m, Matrix<double> v, Matrix<double> k)
-        {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(m, v, k))
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _m = m;
-            _v = v;
-            _k = k;
-        }
-
         /// <summary>
         /// Checks whether the parameters of the distribution are valid. 
         /// </summary>
@@ -196,21 +144,62 @@ namespace MathNet.Numerics.Distributions
             return true;
         }
 
+        /// <summary>
+        /// Sets the parameters of the distribution after checking their validity.
+        /// </summary>
+        /// <param name="m">The mean of the matrix normal.</param>
+        /// <param name="v">The covariance matrix for the rows.</param>
+        /// <param name="k">The covariance matrix for the columns.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(Matrix<double> m, Matrix<double> v, Matrix<double> k)
+        {
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(m, v, k))
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            _m = m;
+            _v = v;
+            _k = k;
+        }
+
         /// <summary>
         /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
         public System.Random RandomSource
         {
             get { return _random; }
-            set
+            set { _random = value ?? new System.Random(); }
-            {
+        }
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
 
-                _random = value;
+        /// <summary>
-            }
+        /// Gets or sets the mean. (M)
+        /// </summary>
+        /// <value>The mean of the distribution.</value>
+        public Matrix<double> Mean
+        {
+            get { return _m; }
+            set { SetParameters(value, _v, _k); }
+        }
+
+        /// <summary>
+        /// Gets or sets the row covariance. (V)
+        /// </summary>
+        /// <value>The row covariance.</value>
+        public Matrix<double> RowCovariance
+        {
+            get { return _v; }
+            set { SetParameters(_m, value, _k); }
+        }
+
+        /// <summary>
+        /// Gets or sets the column covariance. (K)
+        /// </summary>
+        /// <value>The column covariance.</value>
+        public Matrix<double> ColumnCovariance
+        {
+            get { return _k; }
+            set { SetParameters(_m, _v, value); }
         }
 
         /// <summary>

src/Numerics/Distributions/Multinomial.cs

@@ -50,8 +50,10 @@ namespace MathNet.Numerics.Distributions
     /// <para>The statistics classes will check all the incoming parameters whether they are in the allowed
     /// range. This might involve heavy computation. Optionally, by setting Control.CheckDistributionParameters
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
-    public class Multinomial
+    public class Multinomial : IDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// Stores the normalized multinomial probabilities.
         /// </summary>
@@ -60,12 +62,7 @@ namespace MathNet.Numerics.Distributions
         /// <summary>
         /// The number of trials.
         /// </summary>
-        int _n;
+        int _trials;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
 
         /// <summary>
         /// Initializes a new instance of the Multinomial class.
@@ -130,7 +127,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>a string representation of the distribution.</returns>
         public override string ToString()
         {
-            return "Multinomial(Dimension = " + _p.Length + ", Number of Trails = " + _n + ")";
+            return "Multinomial(Dimension = " + _p.Length + ", Number of Trails = " + _trials + ")";
         }
 
         /// <summary>
@@ -177,7 +174,16 @@ namespace MathNet.Numerics.Distributions
             }
 
             _p = (double[]) p.Clone();
-            _n = n;
+            _trials = n;
+        }
+
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -186,7 +192,7 @@ namespace MathNet.Numerics.Distributions
         public double[] P
         {
             get { return (double[]) _p.Clone(); }
-            set { SetParameters(value, _n); }
+            set { SetParameters(value, _trials); }
         }
 
         /// <summary>
@@ -194,33 +200,16 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public int N
         {
-            get { return _n; }
+            get { return _trials; }
             set { SetParameters(_p, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>
         public Vector<double> Mean
         {
-            get { return _n*(DenseVector) P; }
+            get { return _trials*(DenseVector) P; }
         }
 
         /// <summary>
@@ -234,7 +223,7 @@ namespace MathNet.Numerics.Distributions
                 var res = (DenseVector) P;
                 for (var i = 0; i < res.Count; i++)
                 {
-                    res[i] *= _n*(1 - res[i]);
+                    res[i] *= _trials*(1 - res[i]);
                 }
 
                 return res;
@@ -252,7 +241,7 @@ namespace MathNet.Numerics.Distributions
                 var res = (DenseVector) P;
                 for (var i = 0; i < res.Count; i++)
                 {
-                    res[i] = (1.0 - (2.0*res[i]))/Math.Sqrt(_n*(1.0 - res[i])*res[i]);
+                    res[i] = (1.0 - (2.0*res[i]))/Math.Sqrt(_trials*(1.0 - res[i])*res[i]);
                 }
 
                 return res;
@@ -278,9 +267,9 @@ namespace MathNet.Numerics.Distributions
                 throw new ArgumentException(Resources.ArgumentVectorsSameLength, "x");
             }
 
-            if (x.Sum() == _n)
+            if (x.Sum() == _trials)
             {
-                var coef = SpecialFunctions.Multinomial(_n, x);
+                var coef = SpecialFunctions.Multinomial(_trials, x);
                 var num = 1.0;
                 for (var i = 0; i < x.Length; i++)
                 {
@@ -312,9 +301,9 @@ namespace MathNet.Numerics.Distributions
                 throw new ArgumentException(Resources.ArgumentVectorsSameLength, "x");
             }
 
-            if (x.Sum() == _n)
+            if (x.Sum() == _trials)
             {
-                var coef = Math.Log(SpecialFunctions.Multinomial(_n, x));
+                var coef = Math.Log(SpecialFunctions.Multinomial(_trials, x));
                 var num = x.Select((t, i) => t*Math.Log(_p[i])).Sum();
                 return coef + num;
             }
@@ -328,7 +317,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>the counts for each of the different possible values.</returns>
         public int[] Sample()
         {
-            return Sample(RandomSource, _p, _n);
+            return Sample(RandomSource, _p, _trials);
         }
 
         /// <summary>
@@ -339,7 +328,7 @@ namespace MathNet.Numerics.Distributions
         {
             while (true)
             {
-                yield return Sample(RandomSource, _p, _n);
+                yield return Sample(RandomSource, _p, _trials);
             }
         }
 

src/Numerics/Distributions/NegativeBinomial.cs

@@ -48,27 +48,21 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class NegativeBinomial : IDiscreteDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// The r parameter of the distribution.
+
-        /// </summary>
+        double _trials;
-        double _r;
 
         /// <summary>
         /// The p parameter of the distribution.
         /// </summary>
         double _p;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Gets or sets the number of trials.
         /// </summary>
         public double R
         {
-            get { return _r; }
+            get { return _trials; }
             set { SetParameters(value, _p); }
         }
 
@@ -78,7 +72,7 @@ namespace MathNet.Numerics.Distributions
         public double P
         {
             get { return _p; }
-            set { SetParameters(_r, value); }
+            set { SetParameters(_trials, value); }
         }
 
         /// <summary>
@@ -105,20 +99,14 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// Returns a <see cref="System.String"/> that represents this instance.
         /// </summary>
-        /// <param name="r">The number of trials.</param>
+        /// <returns>
-        /// <param name="p">The probability of a trial resulting in success.</param>
+        /// A <see cref="System.String"/> that represents this instance.
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        /// </returns>
-        void SetParameters(double r, double p)
+        public override string ToString()
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(r, p))
+            return "NegativeBinomial(R = " + _trials + ", P = " + _p + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _p = p;
-            _r = r;
         }
 
         /// <summary>
@@ -133,39 +121,36 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        /// <returns>
+        /// <param name="r">The number of trials.</param>
-        /// A <see cref="System.String"/> that represents this instance.
+        /// <param name="p">The probability of a trial resulting in success.</param>
-        /// </returns>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
-        public override string ToString()
+        void SetParameters(double r, double p)
         {
-            return "NegativeBinomial(R = " + _r + ", P = " + _p + ")";
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(r, p))
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            _p = p;
+            _trials = r;
         }
 
         /// <summary>
-        /// Gets or sets the distribution's random number generator.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
         public System.Random RandomSource
         {
             get { return _random; }
-            set
+            set { _random = value ?? new System.Random(); }
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
         }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>
         public double Mean
         {
-            get { return _r*(1.0 - _p)/_p; }
+            get { return _trials*(1.0 - _p)/_p; }
         }
 
         /// <summary>
@@ -173,7 +158,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double Variance
         {
-            get { return _r*(1.0 - _p)/(_p*_p); }
+            get { return _trials*(1.0 - _p)/(_p*_p); }
         }
 
         /// <summary>
@@ -181,7 +166,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double StdDev
         {
-            get { return Math.Sqrt(_r*(1.0 - _p))/_p; }
+            get { return Math.Sqrt(_trials*(1.0 - _p))/_p; }
         }
 
         /// <summary>
@@ -197,7 +182,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double Skewness
         {
-            get { return (2.0 - _p)/Math.Sqrt(_r*(1.0 - _p)); }
+            get { return (2.0 - _p)/Math.Sqrt(_trials*(1.0 - _p)); }
         }
 
         /// <summary>
@@ -205,7 +190,7 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public int Mode
         {
-            get { return _r > 1.0 ? (int) Math.Floor((_r - 1.0)*(1.0 - _p)/_p) : 0; }
+            get { return _trials > 1.0 ? (int) Math.Floor((_trials - 1.0)*(1.0 - _p)/_p) : 0; }
         }
 
         /// <summary>
@@ -239,10 +224,10 @@ namespace MathNet.Numerics.Distributions
         /// <returns>the probability mass at location <paramref name="k"/>.</returns>
         public double Probability(int k)
         {
-            var ln = SpecialFunctions.GammaLn(_r + k)
+            var ln = SpecialFunctions.GammaLn(_trials + k)
-                     - SpecialFunctions.GammaLn(_r)
+                     - SpecialFunctions.GammaLn(_trials)
                      - SpecialFunctions.GammaLn(k + 1.0)
-                     + (_r*Math.Log(_p))
+                     + (_trials*Math.Log(_p))
                      + (k*Math.Log(1.0 - _p));
             return Math.Exp(ln);
         }
@@ -254,10 +239,10 @@ namespace MathNet.Numerics.Distributions
         /// <returns>the log probability mass at location <paramref name="k"/>.</returns>
         public double ProbabilityLn(int k)
         {
-            var ln = SpecialFunctions.GammaLn(_r + k)
+            var ln = SpecialFunctions.GammaLn(_trials + k)
-                     - SpecialFunctions.GammaLn(_r)
+                     - SpecialFunctions.GammaLn(_trials)
                      - SpecialFunctions.GammaLn(k + 1.0)
-                     + (_r*Math.Log(_p))
+                     + (_trials*Math.Log(_p))
                      + (k*Math.Log(1.0 - _p));
             return ln;
         }
@@ -269,7 +254,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>the cumulative distribution at location <paramref name="x"/>.</returns>
         public double CumulativeDistribution(double x)
         {
-            return 1 - SpecialFunctions.BetaRegularized(x + 1, _r, 1 - _p);
+            return 1 - SpecialFunctions.BetaRegularized(x + 1, _trials, 1 - _p);
         }
 
         /// <summary>
@@ -299,7 +284,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>a sample from the distribution.</returns>
         public int Sample()
         {
-            return SampleUnchecked(RandomSource, _r, _p);
+            return SampleUnchecked(RandomSource, _trials, _p);
         }
 
         /// <summary>
@@ -310,7 +295,7 @@ namespace MathNet.Numerics.Distributions
         {
             while (true)
             {
-                yield return SampleUnchecked(RandomSource, _r, _p);
+                yield return SampleUnchecked(RandomSource, _trials, _p);
             }
         }
 

src/Numerics/Distributions/Normal.cs

@@ -47,21 +47,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Normal : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Keeps track of the mean of the normal distribution.
-        /// </summary>
-        double _mean;
 
-        /// <summary>
+        double _mean;
-        /// Keeps track of the standard deviation of the normal distribution.
-        /// </summary>
         double _stdDev;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the Normal class. This is a normal distribution with mean 0.0
         /// and standard deviation 1.0. The distribution will
@@ -190,6 +180,15 @@ namespace MathNet.Numerics.Distributions
             _stdDev = stddev;
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the precision of the normal distribution.
         /// </summary>
@@ -211,23 +210,6 @@ namespace MathNet.Numerics.Distributions
             }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets or sets the mean of the normal distribution.
         /// </summary>

src/Numerics/Distributions/NormalGamma.cs

@@ -100,33 +100,15 @@ namespace MathNet.Numerics.Distributions
     /// <para>The statistics classes will check all the incoming parameters whether they are in the allowed
     /// range. This might involve heavy computation. Optionally, by setting Control.CheckDistributionParameters
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
-    public class NormalGamma
+    public class NormalGamma : IDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// The location of the mean.
-        /// </summary>
-        double _meanLocation;
 
-        /// <summary>
+        double _meanLocation;
-        /// The scale of the mean.
-        /// </summary>
         double _meanScale;
-
-        /// <summary>
-        /// The shape of the precision.
-        /// </summary>
         double _precisionShape;
-
-        /// <summary>
-        /// The inverse scale of the precision.
-        /// </summary>
         double _precisionInvScale;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="NormalGamma"/> class. 
         /// </summary>
@@ -154,6 +136,16 @@ namespace MathNet.Numerics.Distributions
             SetParameters(meanLocation, meanScale, precisionShape, precisionInverseScale);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "NormalGamma(Mean Location = " + _meanLocation + ", Mean Scale = " + _meanScale +
+                   ", Precision Shape = " + _precisionShape + ", Precision Inverse Scale = " + _precisionInvScale + ")";
+        }
+
         /// <summary>
         /// Checks whether the parameters of the distribution are valid. 
         /// </summary>
@@ -189,13 +181,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// A string representation of the distribution.
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
+        public System.Random RandomSource
-        public override string ToString()
         {
-            return "NormalGamma(Mean Location = " + _meanLocation + ", Mean Scale = " + _meanScale +
+            get { return _random; }
-                   ", Precision Shape = " + _precisionShape + ", Precision Inverse Scale = " + _precisionInvScale + ")";
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -234,23 +225,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_meanLocation, _meanScale, _precisionShape, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Returns the marginal distribution for the mean of the <c>NormalGamma</c> distribution.
         /// </summary>

src/Numerics/Distributions/Pareto.cs

@@ -48,21 +48,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Pareto : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// The scale parameter of the distribution.
-        /// </summary>
-        double _scale;
 
-        /// <summary>
+        double _scale;
-        /// The shape parameter of the distribution.
-        /// </summary>
         double _shape;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Pareto"/> class. 
         /// </summary>
@@ -88,6 +78,26 @@ namespace MathNet.Numerics.Distributions
             SetParameters(scale, shape);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "Pareto(Scale = " + _scale + ", Shape = " + _shape + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid. 
+        /// </summary>
+        /// <param name="scale">The scale parameter of the distribution.</param>
+        /// <param name="shape">The shape parameter of the distribution.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double scale, double shape)
+        {
+            return scale > 0.0 && shape > 0.0;
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -106,14 +116,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid. 
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="scale">The scale parameter of the distribution.</param>
+        public System.Random RandomSource
-        /// <param name="shape">The shape parameter of the distribution.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double scale, double shape)
         {
-            return scale > 0.0 && shape > 0.0;
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -134,32 +142,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_scale, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Pareto(Scale = " + _scale + ", Shape = " + _shape + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/Poisson.cs

@@ -44,16 +44,10 @@ namespace MathNet.Numerics.Distributions
     /// </remarks>
     public class Poisson : IDiscreteDistribution
     {
-        /// <summary>
-        /// The Poisson distribution parameter λ.
-        /// </summary>
-        double _lambda;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _lambda;
+
         /// <summary>
         /// Gets or sets the Poisson distribution parameter λ.
         /// </summary>
@@ -87,18 +81,14 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// Returns a <see cref="System.String"/> that represents this instance.
         /// </summary>
-        /// <param name="lambda">The mean (λ) of the distribution.</param>
+        /// <returns>
-        /// <exception cref="System.ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        /// A <see cref="System.String"/> that represents this instance.
-        void SetParameters(double lambda)
+        /// </returns>
+        public override string ToString()
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(lambda))
+            return "Poisson(λ = " + _lambda + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _lambda = lambda;
         }
 
         /// <summary>
@@ -112,14 +102,18 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Returns a <see cref="System.String"/> that represents this instance.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        /// <returns>
+        /// <param name="lambda">The mean (λ) of the distribution.</param>
-        /// A <see cref="System.String"/> that represents this instance.
+        /// <exception cref="System.ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
-        /// </returns>
+        void SetParameters(double lambda)
-        public override string ToString()
         {
-            return "Poisson(λ = " + _lambda + ")";
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(lambda))
+            {
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
+
+            _lambda = lambda;
         }
 
         /// <summary>
@@ -128,15 +122,7 @@ namespace MathNet.Numerics.Distributions
         public System.Random RandomSource
         {
             get { return _random; }
-            set
+            set { _random = value ?? new System.Random(); }
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
         }
 
         /// <summary>

src/Numerics/Distributions/Rayleigh.cs

@@ -49,16 +49,10 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Rayleigh : IContinuousDistribution
     {
-        /// <summary>
-        /// The scale parameter of the distribution.
-        /// </summary>
-        double _scale;
-
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
         System.Random _random;
 
+        double _scale;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Rayleigh"/> class. 
         /// </summary>
@@ -83,18 +77,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Sets the parameters of the distribution after checking their validity.
+        /// A string representation of the distribution.
         /// </summary>
-        /// <param name="scale">The scale parameter of the distribution.</param>
+        /// <returns>a string representation of the distribution.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        public override string ToString()
-        void SetParameters(double scale)
         {
-            if (Control.CheckDistributionParameters && !IsValidParameterSet(scale))
+            return "Rayleigh(Scale = " + _scale + ")";
-            {
-                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
-            }
-
-            _scale = scale;
         }
 
         /// <summary>
@@ -108,21 +96,18 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Gets or sets the scale parameter of the distribution.
+        /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
-        public double Scale
+        /// <param name="scale">The scale parameter of the distribution.</param>
+        /// <exception cref="ArgumentOutOfRangeException">When the parameters don't pass the <see cref="IsValidParameterSet"/> function.</exception>
+        void SetParameters(double scale)
         {
-            get { return _scale; }
+            if (Control.CheckDistributionParameters && !IsValidParameterSet(scale))
-            set { SetParameters(value); }
+            {
-        }
+                throw new ArgumentOutOfRangeException(Resources.InvalidDistributionParameters);
+            }
 
-        /// <summary>
+            _scale = scale;
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Rayleigh(Scale = " + _scale + ")";
         }
 
         /// <summary>
@@ -131,15 +116,16 @@ namespace MathNet.Numerics.Distributions
         public System.Random RandomSource
         {
             get { return _random; }
-            set
+            set { _random = value ?? new System.Random(); }
-            {
+        }
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
 
-                _random = value;
+        /// <summary>
-            }
+        /// Gets or sets the scale parameter of the distribution.
+        /// </summary>
+        public double Scale
+        {
+            get { return _scale; }
+            set { SetParameters(value); }
         }
 
         /// <summary>

src/Numerics/Distributions/Stable.cs

@@ -49,6 +49,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Stable : IContinuousDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The stability parameter of the distribution.
         /// </summary>
@@ -59,21 +61,9 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         double _beta;
 
-        /// <summary>
-        /// The scale parameter of the distribution.
-        /// </summary>
         double _scale;
-
-        /// <summary>
-        /// The location parameter of the distribution.
-        /// </summary>
         double _location;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Stable"/> class. 
         /// </summary>
@@ -101,6 +91,28 @@ namespace MathNet.Numerics.Distributions
             SetParameters(alpha, beta, scale, location);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "Stable(" + "Stability = " + _alpha + ", Skewness = " + _beta + ", Scale = " + _scale + ", Location = " + _location + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid. 
+        /// </summary>
+        /// <param name="alpha">The stability parameter of the distribution.</param>
+        /// <param name="beta">The skewness parameter of the distribution.</param>
+        /// <param name="scale">The scale parameter of the distribution.</param>
+        /// <param name="location">The location parameter of the distribution.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double alpha, double beta, double scale, double location)
+        {
+            return alpha > 0.0 && alpha <= 2.0 && beta >= -1.0 && beta <= 1.0 && scale > 0.0 && !Double.IsNaN(location);
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -122,16 +134,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid. 
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="alpha">The stability parameter of the distribution.</param>
+        public System.Random RandomSource
-        /// <param name="beta">The skewness parameter of the distribution.</param>
-        /// <param name="scale">The scale parameter of the distribution.</param>
-        /// <param name="location">The location parameter of the distribution.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double alpha, double beta, double scale, double location)
         {
-            return alpha > 0.0 && alpha <= 2.0 && beta >= -1.0 && beta <= 1.0 && scale > 0.0 && !Double.IsNaN(location);
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -170,32 +178,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_alpha, _beta, _scale, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Stable(" + "Stability = " + _alpha + ", Skewness = " + _beta + ", Scale = " + _scale + ", Location = " + _location + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Distributions/StudentT.cs

@@ -57,25 +57,11 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class StudentT : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Keeps track of the location of the Student t-distribution.
-        /// </summary>
-        double _location;
-
-        /// <summary>
-        /// Keeps track of the degrees of freedom for the Student t-distribution.
-        /// </summary>
-        double _dof;
 
-        /// <summary>
+        double _location;
-        /// Keeps track of the scale for the Student t-distribution.
-        /// </summary>
         double _scale;
-
+        double _freedom;
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
 
         /// <summary>
         /// Initializes a new instance of the StudentT class. This is a Student t-distribution with location 0.0
@@ -122,7 +108,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>a string representation of the distribution.</returns>
         public override string ToString()
         {
-            return "StudentT(Location = " + _location + ", Scale = " + _scale + ", DoF = " + _dof + ")";
+            return "StudentT(Location = " + _location + ", Scale = " + _scale + ", DoF = " + _freedom + ")";
         }
 
         /// <summary>
@@ -153,7 +139,16 @@ namespace MathNet.Numerics.Distributions
 
             _location = location;
             _scale = scale;
-            _dof = dof;
+            _freedom = dof;
+        }
+
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -162,7 +157,7 @@ namespace MathNet.Numerics.Distributions
         public double Location
         {
             get { return _location; }
-            set { SetParameters(value, _scale, _dof); }
+            set { SetParameters(value, _scale, _freedom); }
         }
 
         /// <summary>
@@ -171,7 +166,7 @@ namespace MathNet.Numerics.Distributions
         public double Scale
         {
             get { return _scale; }
-            set { SetParameters(_location, value, _dof); }
+            set { SetParameters(_location, value, _freedom); }
         }
 
         /// <summary>
@@ -179,33 +174,16 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         public double DegreesOfFreedom
         {
-            get { return _dof; }
+            get { return _freedom; }
             set { SetParameters(_location, _scale, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the Student t-distribution.
         /// </summary>
         public double Mean
         {
-            get { return _dof > 1.0 ? _location : Double.NaN; }
+            get { return _freedom > 1.0 ? _location : Double.NaN; }
         }
 
         /// <summary>
@@ -215,17 +193,17 @@ namespace MathNet.Numerics.Distributions
         {
             get
             {
-                if (Double.IsPositiveInfinity(_dof))
+                if (Double.IsPositiveInfinity(_freedom))
                 {
                     return _scale*_scale;
                 }
 
-                if (_dof > 2.0)
+                if (_freedom > 2.0)
                 {
-                    return _dof*_scale*_scale/(_dof - 2.0);
+                    return _freedom*_scale*_scale/(_freedom - 2.0);
                 }
 
-                return _dof > 1.0 ? Double.PositiveInfinity : Double.NaN;
+                return _freedom > 1.0 ? Double.PositiveInfinity : Double.NaN;
             }
         }
 
@@ -236,17 +214,17 @@ namespace MathNet.Numerics.Distributions
         {
             get
             {
-                if (Double.IsPositiveInfinity(_dof))
+                if (Double.IsPositiveInfinity(_freedom))
                 {
                     return Math.Sqrt(_scale*_scale);
                 }
 
-                if (_dof > 2.0)
+                if (_freedom > 2.0)
                 {
-                    return Math.Sqrt(_dof*_scale*_scale/(_dof - 2.0));
+                    return Math.Sqrt(_freedom*_scale*_scale/(_freedom - 2.0));
                 }
 
-                return _dof > 1.0 ? Double.PositiveInfinity : Double.NaN;
+                return _freedom > 1.0 ? Double.PositiveInfinity : Double.NaN;
             }
         }
 
@@ -262,7 +240,7 @@ namespace MathNet.Numerics.Distributions
                     throw new NotSupportedException();
                 }
 
-                return (((_dof + 1.0)/2.0)*(SpecialFunctions.DiGamma((1.0 + _dof)/2.0) - SpecialFunctions.DiGamma(_dof/2.0))) + Math.Log(Math.Sqrt(_dof)*SpecialFunctions.Beta(_dof/2.0, 1.0/2.0));
+                return (((_freedom + 1.0)/2.0)*(SpecialFunctions.DiGamma((1.0 + _freedom)/2.0) - SpecialFunctions.DiGamma(_freedom/2.0))) + Math.Log(Math.Sqrt(_freedom)*SpecialFunctions.Beta(_freedom/2.0, 1.0/2.0));
             }
         }
 
@@ -273,7 +251,7 @@ namespace MathNet.Numerics.Distributions
         {
             get
             {
-                if (_dof <= 3)
+                if (_freedom <= 3)
                 {
                     throw new NotSupportedException();
                 }
@@ -322,15 +300,15 @@ namespace MathNet.Numerics.Distributions
         public double Density(double x)
         {
             // TODO JVG we can probably do a better job for Cauchy special case
-            if (_dof >= 1e+8d)
+            if (_freedom >= 1e+8d)
             {
                 return Normal.Density(_location, _scale, x);
             }
 
             var d = (x - _location)/_scale;
-            return Math.Exp(SpecialFunctions.GammaLn((_dof + 1.0)/2.0) - SpecialFunctions.GammaLn(_dof/2.0))
+            return Math.Exp(SpecialFunctions.GammaLn((_freedom + 1.0)/2.0) - SpecialFunctions.GammaLn(_freedom/2.0))
-                   *Math.Pow(1.0 + (d*d/_dof), -0.5*(_dof + 1.0))
+                   *Math.Pow(1.0 + (d*d/_freedom), -0.5*(_freedom + 1.0))
-                   /Math.Sqrt(_dof*Math.PI)
+                   /Math.Sqrt(_freedom*Math.PI)
                    /_scale;
         }
 
@@ -342,16 +320,16 @@ namespace MathNet.Numerics.Distributions
         public double DensityLn(double x)
         {
             // TODO JVG we can probably do a better job for Cauchy special case
-            if (_dof >= 1e+8d)
+            if (_freedom >= 1e+8d)
             {
                 return Normal.DensityLn(_location, _scale, x);
             }
 
             var d = (x - _location)/_scale;
-            return SpecialFunctions.GammaLn((_dof + 1.0)/2.0)
+            return SpecialFunctions.GammaLn((_freedom + 1.0)/2.0)
-                   - (0.5*((_dof + 1.0)*Math.Log(1.0 + (d*d/_dof))))
+                   - (0.5*((_freedom + 1.0)*Math.Log(1.0 + (d*d/_freedom))))
-                   - SpecialFunctions.GammaLn(_dof/2.0)
+                   - SpecialFunctions.GammaLn(_freedom/2.0)
-                   - (0.5*Math.Log(_dof*Math.PI)) - Math.Log(_scale);
+                   - (0.5*Math.Log(_freedom*Math.PI)) - Math.Log(_scale);
         }
 
         /// <summary>
@@ -362,14 +340,14 @@ namespace MathNet.Numerics.Distributions
         public double CumulativeDistribution(double x)
         {
             // TODO JVG we can probably do a better job for Cauchy special case
-            if (Double.IsPositiveInfinity(_dof))
+            if (Double.IsPositiveInfinity(_freedom))
             {
                 return Normal.CumulativeDistribution(_location, _scale, x);
             }
 
             var k = (x - _location)/_scale;
-            var h = _dof/(_dof + (k*k));
+            var h = _freedom/(_freedom + (k*k));
-            var ib = 0.5*SpecialFunctions.BetaRegularized(_dof/2.0, 0.5, h);
+            var ib = 0.5*SpecialFunctions.BetaRegularized(_freedom/2.0, 0.5, h);
             return x <= _location ? ib : 1.0 - ib;
         }
 
@@ -396,7 +374,7 @@ namespace MathNet.Numerics.Distributions
         /// <returns>a sample from the distribution.</returns>
         public double Sample()
         {
-            return SampleUnchecked(RandomSource, _location, _scale, _dof);
+            return SampleUnchecked(RandomSource, _location, _scale, _freedom);
         }
 
         /// <summary>
@@ -407,7 +385,7 @@ namespace MathNet.Numerics.Distributions
         {
             while (true)
             {
-                yield return SampleUnchecked(RandomSource, _location, _scale, _dof);
+                yield return SampleUnchecked(RandomSource, _location, _scale, _freedom);
             }
         }
 

src/Numerics/Distributions/Weibull.cs

@@ -48,18 +48,13 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Weibull : IContinuousDistribution
     {
-        /// <summary>
+        System.Random _random;
-        /// Weibull shape parameter.
-        /// </summary>
-        double _shape;
 
-        /// <summary>
+        double _shape;
-        /// Weibull inverse scale parameter.
-        /// </summary>
         double _scale;
 
         /// <summary>
-        /// Reusable intermediate result 1 / (<see cref="_scale"/> ^ <see cref="_shape"/>)
+        /// Reusable intermediate result 1 / (_scale ^ _shape)
         /// </summary>
         /// <remarks>
         /// By caching this parameter we can get slightly better numerics precision
@@ -67,11 +62,6 @@ namespace MathNet.Numerics.Distributions
         /// </remarks>
         double _scalePowShapeInv;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the Weibull class.
         /// </summary>
@@ -133,6 +123,15 @@ namespace MathNet.Numerics.Distributions
             _scalePowShapeInv = Math.Pow(scale, -shape);
         }
 
+        /// <summary>
+        /// Gets or sets the random number generator which is used to draw random samples.
+        /// </summary>
+        public System.Random RandomSource
+        {
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
+        }
+
         /// <summary>
         /// Gets or sets the shape of the Weibull distribution.
         /// </summary>
@@ -151,23 +150,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_shape, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the Weibull distribution.
         /// </summary>

src/Numerics/Distributions/Wishart.cs

@@ -50,6 +50,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Wishart
     {
+        System.Random _random;
+
         /// <summary>
         /// The degrees of freedom for the Wishart distribution.
         /// </summary>
@@ -65,11 +67,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         Cholesky<double> _chol;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Wishart"/> class. 
         /// </summary>

src/Numerics/Distributions/Zipf.cs

@@ -49,6 +49,8 @@ namespace MathNet.Numerics.Distributions
     /// to <c>false</c>, all parameter checks can be turned off.</para></remarks>
     public class Zipf : IDiscreteDistribution
     {
+        System.Random _random;
+
         /// <summary>
         /// The s parameter of the distribution.
         /// </summary>
@@ -59,11 +61,6 @@ namespace MathNet.Numerics.Distributions
         /// </summary>
         int _n;
 
-        /// <summary>
-        /// The distribution's random number generator.
-        /// </summary>
-        System.Random _random;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Zipf"/> class. 
         /// </summary>
@@ -87,6 +84,26 @@ namespace MathNet.Numerics.Distributions
             SetParameters(s, n);
         }
 
+        /// <summary>
+        /// A string representation of the distribution.
+        /// </summary>
+        /// <returns>a string representation of the distribution.</returns>
+        public override string ToString()
+        {
+            return "Zipf(S = " + _s + ", N = " + _n + ")";
+        }
+
+        /// <summary>
+        /// Checks whether the parameters of the distribution are valid. 
+        /// </summary>
+        /// <param name="s">The s parameter of the distribution.</param>
+        /// <param name="n">The n parameter of the distribution.</param>
+        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
+        static bool IsValidParameterSet(double s, int n)
+        {
+            return n > 0 && s > 0.0;
+        }
+
         /// <summary>
         /// Sets the parameters of the distribution after checking their validity.
         /// </summary>
@@ -104,14 +121,12 @@ namespace MathNet.Numerics.Distributions
         }
 
         /// <summary>
-        /// Checks whether the parameters of the distribution are valid. 
+        /// Gets or sets the random number generator which is used to draw random samples.
         /// </summary>
-        /// <param name="s">The s parameter of the distribution.</param>
+        public System.Random RandomSource
-        /// <param name="n">The n parameter of the distribution.</param>
-        /// <returns><c>true</c> when the parameters are valid, <c>false</c> otherwise.</returns>
-        static bool IsValidParameterSet(double s, int n)
         {
-            return n > 0 && s > 0.0;
+            get { return _random; }
+            set { _random = value ?? new System.Random(); }
         }
 
         /// <summary>
@@ -132,32 +147,6 @@ namespace MathNet.Numerics.Distributions
             set { SetParameters(_s, value); }
         }
 
-        /// <summary>
-        /// A string representation of the distribution.
-        /// </summary>
-        /// <returns>a string representation of the distribution.</returns>
-        public override string ToString()
-        {
-            return "Zipf(S = " + _s + ", N = " + _n + ")";
-        }
-
-        /// <summary>
-        /// Gets or sets the random number generator which is used to draw random samples.
-        /// </summary>
-        public System.Random RandomSource
-        {
-            get { return _random; }
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException();
-                }
-
-                _random = value;
-            }
-        }
-
         /// <summary>
         /// Gets the mean of the distribution.
         /// </summary>

src/Numerics/Numerics.csproj

@@ -95,6 +95,7 @@
     <Compile Include="Distributions\ChiSquare.cs" />
     <Compile Include="Distributions\ContinuousUniform.cs" />
     <Compile Include="Distributions\ConwayMaxwellPoisson.cs" />
+    <Compile Include="Distributions\IDistribution.cs" />
     <Compile Include="Distributions\Dirichlet.cs" />
     <Compile Include="Distributions\DiscreteUniform.cs" />
     <Compile Include="Distributions\Erlang.cs" />

src/UnitTests/DistributionTests/CommonDistributionTests.cs

@@ -160,22 +160,19 @@ namespace MathNet.Numerics.UnitTests.DistributionTests
             }
         }
 
-        /// <summary>
-        /// Fail set random source with <c>null</c> reference.
-        /// </summary>
         [Test]
-        public void FailSetRandomSourceWithNullReference()
+        public void HasRandomSourceEvenAfterSetToNull()
         {
             foreach (var dd in _discreteDistributions)
             {
-                var dd1 = dd;
+                Assert.DoesNotThrow(() => dd.RandomSource = null);
-                Assert.Throws<ArgumentNullException>(() => dd1.RandomSource = null);
+                Assert.IsNotNull(dd.RandomSource);
             }
 
             foreach (var cd in _continuousDistributions)
             {
-                var cd1 = cd;
+                Assert.DoesNotThrow(() => cd.RandomSource = null);
-                Assert.Throws<ArgumentNullException>(() => cd1.RandomSource = null);
+                Assert.IsNotNull(cd.RandomSource);
             }
         }
 

src/UnitTests/DistributionTests/Multivariate/DirichletTests.cs

@@ -114,14 +114,12 @@ namespace MathNet.Numerics.UnitTests.DistributionTests.Multivariate
             };
         }
 
-        /// <summary>
-        /// Fail set random source with <c>null</c> reference.
-        /// </summary>
         [Test]
-        public void FailSetRandomSourceWithNullReference()
+        public void HasRandomSourceEvenAfterSetToNull()
         {
             var d = new Dirichlet(0.3, 5);
-            Assert.Throws<ArgumentNullException>(() => d.RandomSource = null);
+            Assert.DoesNotThrow(() => d.RandomSource = null);
+            Assert.IsNotNull(d.RandomSource);
         }
 
         /// <summary>

src/UnitTests/DistributionTests/Multivariate/InverseWishartTests.cs

@@ -121,14 +121,12 @@ namespace MathNet.Numerics.UnitTests.DistributionTests.Multivariate
             };
         }
 
-        /// <summary>
-        /// Fail set random source with <c>null</c> reference.
-        /// </summary>
         [Test]
-        public void FailSetRandomSourceWithNullReference()
+        public void HasRandomSourceEvenAfterSetToNull()
         {
             var d = new InverseWishart(1.0, MatrixLoader.GenerateRandomPositiveDefiniteDenseMatrix(2));
-            Assert.Throws<ArgumentNullException>(() => d.RandomSource = null);
+            Assert.DoesNotThrow(() => d.RandomSource = null);
+            Assert.IsNotNull(d.RandomSource);
         }
 
         /// <summary>

src/UnitTests/DistributionTests/Multivariate/MatrixNormalTests.cs

@@ -130,16 +130,14 @@ namespace MathNet.Numerics.UnitTests.DistributionTests.Multivariate
             };
         }
 
-        /// <summary>
-        /// Fail set random source with <c>null</c> reference.
-        /// </summary>
         [Test]
-        public void FailSetRandomSourceWithNullReference()
+        public void HasRandomSourceEvenAfterSetToNull()
         {
             const int N = 2;
             const int P = 3;
             var d = new MatrixNormal(MatrixLoader.GenerateRandomDenseMatrix(N, P), MatrixLoader.GenerateRandomPositiveDefiniteDenseMatrix(N), MatrixLoader.GenerateRandomPositiveDefiniteDenseMatrix(P));
-            Assert.Throws<ArgumentNullException>(() => d.RandomSource = null);
+            Assert.DoesNotThrow(() => d.RandomSource = null);
+            Assert.IsNotNull(d.RandomSource);
         }
 
         /// <summary>