Added AbsoluteMaximum, AbsoluteMaximumIndex and fixed a bug with Random method.

src/Numerics/LinearAlgebra/Double/DenseVector.cs

@@ -770,6 +770,45 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             return index;
         }
 
+        /// <summary>
+        /// Returns the value of the absolute minimum element.
+        /// </summary>
+        /// <returns>The value of the absolute minimum element.</returns>
+        public override double AbsoluteMinimum()
+        {
+            return Math.Abs(this.Data[this.AbsoluteMinimumIndex()]);
+        }
+
+        /// <summary>
+        /// Returns the value of the absolute maximum element.
+        /// </summary>
+        /// <returns>The value of the absolute maximum element.</returns>
+        public override double AbsoluteMaximum()
+        {
+            return Math.Abs(this.Data[this.AbsoluteMaximumIndex()]);
+        }
+
+        /// <summary>
+        /// Returns the index of the absolute maximum element.
+        /// </summary>
+        /// <returns>The index of absolute maximum element.</returns>   
+        public override int AbsoluteMaximumIndex()
+        {
+            var index = 0;
+            var max = Math.Abs(this.Data[index]);
+            for (var i = 1; i < this.Count; i++)
+            {
+                var test = Math.Abs(this.Data[i]);
+                if (test > max)
+                {
+                    index = i;
+                    max = test;
+                }
+            }
+
+            return index;
+        }
+
         /// <summary>
         /// Creates a vector containing specified elements.
         /// </summary>
@@ -1101,7 +1140,7 @@ namespace MathNet.Numerics.LinearAlgebra.Double
         /// <exception cref="ArgumentNullException">If the n vector is non poisitive<see langword="null" />.</exception> 
         public override Vector Random(int length, IContinuousDistribution randomDistribution)
         {
-            if (length < 0)
+            if (length < 1)
             {
                 throw new ArgumentException(Resources.ArgumentMustBePositive, "length");
             }
@@ -1127,7 +1166,7 @@ namespace MathNet.Numerics.LinearAlgebra.Double
         /// <exception cref="ArgumentNullException">If the n vector is non poisitive<see langword="null" />.</exception> 
         public override Vector Random(int length, IDiscreteDistribution randomDistribution)
         {
-            if (length < 0)
+            if (length < 1)
             {
                 throw new ArgumentException(Resources.ArgumentMustBePositive, "length");
             }

src/Numerics/LinearAlgebra/Double/Vector.cs

@@ -810,6 +810,36 @@ namespace MathNet.Numerics.LinearAlgebra.Double
             return index;
         }
 
+        /// <summary>
+        /// Returns the value of the absolute maximum element.
+        /// </summary>
+        /// <returns>The value of the absolute maximum element.</returns>
+        public virtual double AbsoluteMaximum()
+        {
+            return Math.Abs(this[this.AbsoluteMaximumIndex()]);
+        }
+
+        /// <summary>
+        /// Returns the index of the absolute maximum element.
+        /// </summary>
+        /// <returns>The index of absolute maximum element.</returns>   
+        public virtual int AbsoluteMaximumIndex()
+        {
+            var index = 0;
+            var max = Math.Abs(this[index]);
+            for (var i = 1; i < this.Count; i++)
+            {
+                var test = Math.Abs(this[i]);
+                if (test > max)
+                {
+                    index = i;
+                    max = test;
+                }
+            }
+
+            return index;
+        }
+
         /// <summary>
         /// Returns the value of maximum element.
         /// </summary>

src/UnitTests/LinearAlgebraTests/Double/VectorTests.cs

@@ -296,6 +296,24 @@ namespace MathNet.Numerics.UnitTests.LinearAlgebraTests.Double
             Assert.AreEqual(expected, actual);
         }
 
+        [Test]
+        public void CanFindAbsoluteMaximumIndex()
+        {
+            var source = this.CreateVector(this._data);
+            var expected = 0;
+            var actual = source.AbsoluteMaximumIndex();
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        public void CanFindAbsoluteMaximum()
+        {
+            var source = this.CreateVector(this._data);
+            double expected = 1;
+            var actual = source.AbsoluteMaximum();
+            Assert.AreEqual(expected, actual);
+        }
+
         [Test]
         public void CanFindMaximumIndex()
         {