Merge pull request #68 from ArtyomBaranovskiy/statistics-kurtosis

Statistics: DescriptiveStatistics Kurtosis fix, I18N test fix

src/Numerics/Statistics/DescriptiveStatistics.cs

@@ -357,10 +357,8 @@ namespace MathNet.Numerics.Statistics
 
                     if (n > 3)
                     {
-                        Kurtosis = (((double)n * (n + 1))
-                                    / ((n - 1) * (n - 2) * (n - 3))
-                                    * (kurtosis / (Variance * Variance)))
-                                   - ((3.0 * (n - 1) * (n - 1)) / ((n - 2) * (n - 3)));
+                        Kurtosis = ((double)n * n - 1) / ((n - 2) * (n - 3))
+                            * (n * kurtosis / (variance * variance) - 3 + 6.0 / (n + 1));
                     }
                 }
             }

src/UnitTests/StatisticsTests/DescriptiveStatisticsTests.cs

@@ -66,6 +66,8 @@ namespace MathNet.Numerics.UnitTests.StatisticsTests
             _data.Add("numacc3", numacc3);
             var numacc4 = new StatTestData("./data/NIST/NumAcc4.dat");
             _data.Add("numacc4", numacc4);
+            var meixner = new StatTestData("./data/NIST/Meixner.dat");
+            _data.Add("meixner", meixner);
         }
 
         /// <summary>
@@ -102,6 +104,7 @@ namespace MathNet.Numerics.UnitTests.StatisticsTests
         [TestCase("numacc2", 13, 0, -2.003003003003, 1.2, 1.1, 1.3, 1001)]
         [TestCase("numacc3", 9, 0, -2.003003003003, 1000000.2, 1000000.1, 1000000.3, 1001)]
         [TestCase("numacc4", 8, 0, -2.00300300299913, 10000000.2, 10000000.1, 10000000.3, 1001)]
+        [TestCase("meixner", 8, -0.016649617280859657, 0.8171318629552635, -0.002042931016531602, -4.825626912281697, 5.3018298664184913, 10000)]
         public void IEnumerableDouble(string dataSet, int digits, double skewness, double kurtosis, double median, double min, double max, int count)
         {
             var data = _data[dataSet];

src/UnitTests/StatisticsTests/StatTestData.cs

@@ -24,6 +24,8 @@
 // OTHER DEALINGS IN THE SOFTWARE.
 // </copyright>
 
+using System.Globalization;
+
 namespace MathNet.Numerics.UnitTests.StatisticsTests
 {
     using System.Collections.Generic;
@@ -87,7 +89,7 @@ namespace MathNet.Numerics.UnitTests.StatisticsTests
                     line = line.Trim();
                     if (!line.Equals(string.Empty))
                     {
-                        list.Add(double.Parse(line));
+                        list.Add(double.Parse(line, CultureInfo.InvariantCulture));
                     }
 
                     line = reader.ReadLine();
@@ -117,7 +119,7 @@ namespace MathNet.Numerics.UnitTests.StatisticsTests
                 return 0;
             }
 
-            return double.Parse(str.Substring(start + 1).Trim());
+            return double.Parse(str.Substring(start + 1).Trim(), CultureInfo.InvariantCulture);
         }
     }
 }

src/UnitTests/UnitTests.csproj

@@ -1065,6 +1065,10 @@
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
     <None Include="App.config" />
+    <None Include="..\..\data\NIST\Meixner.dat">
+      <Link>data\NIST\Meixner.dat</Link>
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Include="packages.config" />
     <None Include="Properties\Settings.settings">
       <Generator>SettingsSingleFileGenerator</Generator>