interpolation: assume samples to be sorted (splines-only)

Signed-off-by: Christoph Ruegg <git@cdrnet.ch>

src/Managed/Interpolation/Algorithms/BarycentricInterpolation.cs

@@ -64,7 +64,7 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         /// <summary>
         /// Initializes a new instance of the BarycentricInterpolation class.
         /// </summary>
-        /// <param name="samplePoints">Sample Points t</param>
+        /// <param name="samplePoints">Sample Points t (no sorting assumed)</param>
         /// <param name="sampleValues">Sample Values x(t)</param>
         /// <param name="barycentricWeights">Barycentric weights w(t)</param>
         public BarycentricInterpolation(
@@ -95,7 +95,7 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         }
 
         /// <summary>
-        /// Initialize the interpolation method with the given sample set.
+        /// Initialize the interpolation method with the given sample set (no sorting assumed).
         /// </summary>
         /// <param name="samplePoints">Sample Points t</param>
         /// <param name="sampleValues">Sample Values x(t)</param>
@@ -153,7 +153,7 @@ namespace MathNet.Numerics.Interpolation.Algorithms
                 return this.values[0];
             }
 
-            // evaluate closest point and offset from that point
+            // evaluate closest point and offset from that point (no sorting assumed)
             int closestPoint = 0;
             double offset = t - this.points[0];
             for (int i = 1; i < this.points.Count; i++)

src/Managed/Interpolation/Algorithms/LinearSplineInterpolation.cs

@@ -55,8 +55,8 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         /// <summary>
         /// Initializes a new instance of the LinearSplineInterpolation class.
         /// </summary>
-        /// <param name="samplePoints">Sample Points t</param>
-        /// <param name="sampleValues">Sample Values x(samplePoints)</param>
+        /// <param name="samplePoints">Sample Points t, sorted ascending.</param>
+        /// <param name="sampleValues">Sample Values x(t)</param>
         public LinearSplineInterpolation(
             IList<double> samplePoints,
             IList<double> sampleValues)
@@ -85,9 +85,9 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         }
 
         /// <summary>
-        /// Initialize the interpolation method with the given spline coefficients.
+        /// Initialize the interpolation method with the given spline coefficients (sorted by the sample points t).
         /// </summary>
-        /// <param name="samplePoints">Sample Points t</param>
+        /// <param name="samplePoints">Sample Points t, sorted ascending.</param>
         /// <param name="sampleValues">Sample Values x(t)</param>
         public void Initialize(
             IList<double> samplePoints,
@@ -114,22 +114,16 @@ namespace MathNet.Numerics.Interpolation.Algorithms
             }
 
             double[] coefficients = new double[4 * (samplePoints.Count - 1)];
-            double[] sortedPoints = new double[samplePoints.Count];
-            samplePoints.CopyTo(sortedPoints, 0);
-            double[] sortedValues = new double[sampleValues.Count];
-            sampleValues.CopyTo(sortedValues, 0);
-
-            /* TODO: Sorting.Sort(sortedPoints, sortedValues); */
 
-            for (int i = 0, j = 0; i < sortedPoints.Length - 1; i++, j += 4)
+            for (int i = 0, j = 0; i < samplePoints.Count - 1; i++, j += 4)
             {
-                coefficients[j] = sortedValues[i];
-                coefficients[j + 1] = (sortedValues[i + 1] - sortedValues[i]) / (sortedPoints[i + 1] - sortedPoints[i]);
+                coefficients[j] = sampleValues[i];
+                coefficients[j + 1] = (sampleValues[i + 1] - sampleValues[i]) / (samplePoints[i + 1] - samplePoints[i]);
                 coefficients[j + 2] = 0;
                 coefficients[j + 3] = 0;
             }
 
-            this.spline.Initialize(sortedPoints, coefficients);
+            this.spline.Initialize(samplePoints, coefficients);
         }
 
         /// <summary>

src/Managed/Interpolation/Algorithms/RationalPoleFreeInterpolation.cs

@@ -90,7 +90,7 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         /// <remarks>
         /// The interpolation scheme order will be set to 3.
         /// </remarks>
-        /// <param name="samplePoints">Sample Points t</param>
+        /// <param name="samplePoints">Sample Points t (no sorting assumed)</param>
         /// <param name="sampleValues">Sample Values x(t)</param>
         public void Initialize(
             IList<double> samplePoints,
@@ -100,7 +100,7 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         }
 
         /// <summary>
-        /// Initialize the interpolation method with the given sample set.
+        /// Initialize the interpolation method with the given sample set (no sorting assumed).
         /// </summary>
         /// <param name="samplePoints">Sample Points t</param>
         /// <param name="sampleValues">Sample Values x(t)</param>

src/Managed/Interpolation/Algorithms/SplineInterpolation.cs

@@ -64,8 +64,8 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         /// <summary>
         /// Initializes a new instance of the SplineInterpolation class.
         /// </summary>
-        /// <param name="samplePoints">Sample Points t (length: N)</param>
-        /// <param name="splineCoefficients">Spline Coefficients (length: 4*(N-1))</param>
+        /// <param name="samplePoints">Sample Points t (length: N), sorted ascending.</param>
+        /// <param name="splineCoefficients">Spline Coefficients (length: 4*(N-1)).</param>
         public SplineInterpolation(
             IList<double> samplePoints,
             IList<double> splineCoefficients)
@@ -93,10 +93,10 @@ namespace MathNet.Numerics.Interpolation.Algorithms
         }
 
         /// <summary>
-        /// Initialize the interpolation method with the given spline coefficients.
+        /// Initialize the interpolation method with the given spline coefficients (sorted by the sample points t).
         /// </summary>
-        /// <param name="samplePoints">Sample Points t (length: N)</param>
-        /// <param name="splineCoefficients">Spline Coefficients (length: 4*(N-1))</param>
+        /// <param name="samplePoints">Sample Points t (length: N), sorted ascending.</param>
+        /// <param name="splineCoefficients">Spline Coefficients (length: 4*(N-1)).</param>
         public void Initialize(
             IList<double> samplePoints,
             IList<double> splineCoefficients)

src/Managed/Interpolation/Interpolation.cs

@@ -54,9 +54,9 @@ namespace MathNet.Numerics.Interpolation
         }
 
         /// <summary>
-        /// Create a linear spline interpolation based on arbitrary points.
+        /// Create a linear spline interpolation based on arbitrary points (sorted ascending).
         /// </summary>
-        /// <param name="points">The sample points t. Supports both lists and arrays.</param>
+        /// <param name="points">The sample points t, sorted ascending. Supports both lists and arrays.</param>
         /// <param name="values">The sample point values x(t). Supports both lists and arrays.</param>
         /// <returns>
         /// An interpolation scheme optimized for the given sample points and values,