interpolation test: now verifying minimum sample count check

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

src/Managed.UnitTests/InterpolationTests/InterpolationContract.cs

@@ -39,17 +39,12 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         where TInterpolation : IInterpolation
     {
         public Func<IList<double>, IList<double>, IInterpolation> Factory { get; set; }
-        public int[] Order { get; set; }
+        public int MinimumSampleCount { get; set; }
         public bool NonStandardParameters { get; set; }
         public bool LinearBehavior { get; set; }
         public bool PolynomialBehavior { get; set; }
         public bool RationalBehavior { get; set; }
 
-        public InterpolationContract()
-        {
-            Order = new[] { 4 };
-        }
-
         protected override IEnumerable<Test> GetContractVerificationTests()
         {
             // Infrastructure Tests
@@ -59,6 +54,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
 
             yield return CreateInitChecksForNullTest("InitChecksForNull");
             yield return CreateInitChecksForMatchingCountTest("InitChecksForMatchingCount");
+            yield return CreateInitChecksForMinimumCountTest("InitChecksForMinimumCount");
 
             if (!NonStandardParameters)
             {
@@ -89,7 +85,10 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         {
             return new TestCase(name, () =>
             {
-                var interpolation = Factory(new List<double> { 1, 2, 3 }, new List<double> { 10, 20, 30 });
+                double[] points, values;
+                SampleFunctionEquidistant(t => 5 + 10 * t, -2.0, 8.0, MinimumSampleCount, out points, out values);
+
+                var interpolation = Factory(points, values);
 
                 AssertionHelper.Verify(() =>
                 {
@@ -139,6 +138,22 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
             });
         }
 
+        private Test CreateInitChecksForMinimumCountTest(string name)
+        {
+            return new TestCase(name, () =>
+            {
+                double[] pointsOk, valuesOk;
+                SampleFunctionEquidistant(t => 5 + 10 * t, -2.0, 8.0, MinimumSampleCount, out pointsOk, out valuesOk);
+
+                Assert.DoesNotThrow(() => Factory(pointsOk, valuesOk));
+
+                double[] pointsFail, valuesFail;
+                SampleFunctionEquidistant(t => 5 + 10 * t, -2.0, 8.0, MinimumSampleCount - 1, out pointsFail, out valuesFail);
+
+                Assert.Throws(typeof(ArgumentOutOfRangeException), () => Factory(pointsFail, valuesFail));
+            });
+        }
+
         private Test CreateConstructorInitShortcutTest(string name)
         {
             return new TestCase(name, () =>
@@ -162,7 +177,10 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         {
             return new TestCase(name, () =>
             {
-                var interpolation = Factory(new List<double> { 1, 2, 3 }, new List<double> { 10, 20, 30 });
+                double[] points, values;
+                SampleFunctionEquidistant(t => 5 + 10 * t, -2.0, 8.0, MinimumSampleCount, out points, out values);
+
+                var interpolation = Factory(points, values);
 
                 // verify consistent differentiation capability
                 if (interpolation.SupportsDifferentiation)
@@ -224,9 +242,11 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
                 const double xOffset = 4.0;
                 Random random = new Random();
 
-                for (int k = 0; k < Order.Length; k++)
+                int[] orders = { MinimumSampleCount, MinimumSampleCount + 1, MinimumSampleCount + 5 };
+
+                for (int k = 0; k < orders.Length; k++)
                 {
-                    int order = Order[k];
+                    int order = orders[k];
 
                     // build linear samples
                     double[] points = new double[order];
@@ -334,6 +354,18 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
             points = new double[samples];
             values = new double[samples];
 
+            if(samples == 0)
+            {
+                return;
+            }
+
+            if(samples == 1)
+            {
+                double t = points[0] = 0.5 * (start + stop);
+                values[0] = f(t);
+                return;
+            }
+
             double step = (stop - start) / (samples - 1);
             for (int i = 0; i < points.Length; i++)
             {

src/Managed.UnitTests/InterpolationTests/InterpolationTest.cs

@@ -43,7 +43,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract NevillePolynomialContractTests = new InterpolationContract<NevillePolynomialInterpolation>()
         {
             Factory = (t, x) => new NevillePolynomialInterpolation(t, x),
-            Order = new[] { 1, 2, 6 },
+            MinimumSampleCount = 1,
             LinearBehavior = true,
             PolynomialBehavior = true,
             RationalBehavior = false
@@ -53,7 +53,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract BulirschStoerRationalContractTests = new InterpolationContract<BulirschStoerRationalInterpolation>()
         {
             Factory = Interpolate.RationalWithPoles,
-            Order = new[] { 1, 2, 6 },
+            MinimumSampleCount = 1,
             LinearBehavior = false,
             PolynomialBehavior = true,
             RationalBehavior = true
@@ -65,7 +65,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract BarycentricContractTests = new InterpolationContract<BarycentricInterpolation>()
         {
             Factory = (t, x) => new BarycentricInterpolation(t, x, FloaterHormannRationalInterpolation.EvaluateBarycentricWeights(t, x, 2)),
-            Order = new[] { 1, 2, 6 },
+            MinimumSampleCount = 3,
             NonStandardParameters = true,
         };
 
@@ -73,7 +73,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract FloaterHormannRationalContractTests = new InterpolationContract<FloaterHormannRationalInterpolation>()
         {
             Factory = Interpolate.RationalWithoutPoles,
-            Order = new[] { 1, 2, 6 },
+            MinimumSampleCount = 1,
             LinearBehavior = true,
             PolynomialBehavior = true,
             RationalBehavior = true
@@ -85,7 +85,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract SplineContractTests = new InterpolationContract<SplineInterpolation>()
         {
             Factory = (t, x) => new SplineInterpolation(t, LinearSplineInterpolation.EvaluateSplineCoefficients(t, x)),
-            Order = new[] { 1, 2, 6 },
+            MinimumSampleCount = 2,
             NonStandardParameters = true,
         };
 
@@ -93,7 +93,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract CubicHermiteSplineContractTests = new InterpolationContract<CubicHermiteSplineInterpolation>()
         {
             Factory = (t, x) => new CubicHermiteSplineInterpolation(t, x, CubicSplineInterpolation.EvaluateSplineDerivatives(t, x, SplineBoundaryCondition.Natural, 0.0, SplineBoundaryCondition.Natural, 0.0)),
-            Order = new[] { 1, 2, 6 },
+            MinimumSampleCount = 2,
             NonStandardParameters = true,
         };
 
@@ -101,7 +101,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract LinearSplineContractTests = new InterpolationContract<LinearSplineInterpolation>()
         {
             Factory = Interpolate.LinearBetweenPoints,
-            Order = new[] { 2, 3, 6 },
+            MinimumSampleCount = 2,
             LinearBehavior = true,
             PolynomialBehavior = false,
             RationalBehavior = false
@@ -111,7 +111,7 @@ namespace MathNet.Numerics.UnitTests.InterpolationTests
         public readonly IContract CubicSplineContractTests = new InterpolationContract<CubicSplineInterpolation>()
         {
             Factory = (t, x) => new CubicSplineInterpolation(t, x),
-            Order = new[] { 2, 3, 6 },
+            MinimumSampleCount = 2,
             LinearBehavior = true,
             PolynomialBehavior = false,
             RationalBehavior = false

src/Managed/Interpolation/Algorithms/BulirschStoerRationalInterpolation.cs

@@ -108,6 +108,11 @@ namespace MathNet.Numerics.Interpolation.Algorithms
                 throw new ArgumentNullException("sampleValues");
             }
 
+            if (samplePoints.Count < 1)
+            {
+                throw new ArgumentOutOfRangeException("samplePoints");
+            }
+
             if (samplePoints.Count != sampleValues.Count)
             {
                 throw new ArgumentException(Properties.Resources.ArgumentVectorsSameLengths);

src/Managed/Interpolation/Algorithms/NevillePolynomialInterpolation.cs

@@ -113,6 +113,11 @@ namespace MathNet.Numerics.Interpolation.Algorithms
                 throw new ArgumentNullException("sampleValues");
             }
 
+            if (samplePoints.Count < 1)
+            {
+                throw new ArgumentOutOfRangeException("samplePoints");
+            }
+
             if (samplePoints.Count != sampleValues.Count)
             {
                 throw new ArgumentException(Properties.Resources.ArgumentVectorsSameLengths);