GH-636: Add an Example for Measures.Correlation Method (Double[][])

accord-net · Sep 24, 2017 · 86c8991 · 86c8991
1 parent 81469bf
commit 86c8991
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Showing 2 changed files with 42 additions and 2 deletions.
diff --git a/Sources/Accord.Math/Accord.Statistics/Measures.Matrix.cs b/Sources/Accord.Math/Accord.Statistics/Measures.Matrix.cs
@@ -1515,6 +1515,15 @@ public static double[][] Scatter(double[][] matrix, double[] means, double divis
         /// </remarks>
         /// <param name="matrix">A multi-dimensional array containing the matrix values.</param>
         /// <returns>The correlation matrix.</returns>
+        /// 
+        /// <example>
+        ///   <code source="Unit Tests\Accord.Tests.Statistics\ToolsTest.cs" region="doc_correlation" />
+        /// </example>
+        /// 
+        /// <example>
+        ///   <code source="Unit Tests\Accord.Tests.Statistics\ToolsTest.cs" region="doc_correlation" />
+        /// </example>
+        /// 
         public static double[,] Correlation(this double[,] matrix)
         {
             double[] means = Mean(matrix, dimension: 0);
@@ -1530,6 +1539,11 @@ public static double[][] Scatter(double[][] matrix, double[] means, double divis
         /// </remarks>
         /// <param name="matrix">A multi-dimensional array containing the matrix values.</param>
         /// <returns>The correlation matrix.</returns>
+        /// 
+        /// <example>
+        ///   <code source="Unit Tests\Accord.Tests.Statistics\ToolsTest.cs" region="doc_correlation" />
+        /// </example>
+        /// 
         public static double[][] Correlation(this double[][] matrix)
         {
             double[] means = Mean(matrix, dimension: 0);
@@ -1551,6 +1565,10 @@ public static double[][] Correlation(this double[][] matrix)
         /// 
         /// <returns>The correlation matrix.</returns>
         /// 
+        /// <example>
+        ///   <code source="Unit Tests\Accord.Tests.Statistics\ToolsTest.cs" region="doc_correlation" />
+        /// </example>
+        /// 
         public static double[,] Correlation(this double[,] matrix, double[] means, double[] standardDeviations)
         {
             int rows = matrix.Rows();
@@ -1593,6 +1611,10 @@ public static double[][] Correlation(this double[][] matrix)
         /// 
         /// <returns>The correlation matrix.</returns>
         /// 
+        /// <example>
+        ///   <code source="Unit Tests\Accord.Tests.Statistics\ToolsTest.cs" region="doc_correlation" />
+        /// </example>
+        /// 
         public static double[][] Correlation(this double[][] matrix, double[] means, double[] standardDeviations)
         {
             int rows = matrix.Rows();

diff --git a/Unit Tests/Accord.Tests.Statistics/ToolsTest.cs b/Unit Tests/Accord.Tests.Statistics/ToolsTest.cs
@@ -974,6 +974,9 @@ public void CorrelationTest()
         {
             // http://www.solvemymath.com/online_math_calculator/statistics/descriptive/correlation.php
 
+            #region doc_correlation
+            // Let's say we have a matrix containing 5
+            // samples (rows) of 3 dimensions (columns):
             double[,] matrix = new double[,]
             {
                 { 4.0, 2.0, 0.60 },
@@ -983,7 +986,10 @@ public void CorrelationTest()
                 { 4.1, 2.2, 0.63 }
             };
 
+            // We can compute their correlation matrix using
+            double[,] corr1 = Measures.Correlation(matrix);
 
+            // The matrix should be equal to:
             double[,] expected = new double[,]
             {
                 { 1.000000, 0.5669467, 0.533745 },
@@ -992,10 +998,22 @@ public void CorrelationTest()
             };
 
 
-            double[,] actual = Measures.Correlation(matrix);
+            // The same could be repeated with a jagged matrix instead:
+            double[][] jagged = new double[][]
+            {
+                new double[] { 4.0, 2.0, 0.60 },
+                new double[] { 4.2, 2.1, 0.59 },
+                new double[] { 3.9, 2.0, 0.58 },
+                new double[] { 4.3, 2.1, 0.62 },
+                new double[] { 4.1, 2.2, 0.63 }
+            };
 
-            Assert.IsTrue(Matrix.IsEqual(expected, actual, 0.001));
+            // And the value would be the same:
+            double[][] corr2 = Measures.Correlation(jagged);
+            #endregion
 
+            Assert.IsTrue(Matrix.IsEqual(expected, corr1, 1e-5));
+            Assert.IsTrue(Matrix.IsEqual(expected, corr2, 1e-5));
         }