Fix variance implementation and add tests to Math package.

refs #34

src/eva2/tools/math/Mathematics.java

@@ -631,9 +631,15 @@ public final class Mathematics {
         for (int i = 0; i < vector.length; i++) {
             result += Math.pow(vector[i] - mean, 2);
         }
-        return result;
+        return result / (vector.length - 1);
     }
 
+    /**
+     * Computes the sample standard deviation.
+     *
+     * @param vector
+     * @return
+     */
     public static double stdDev(double[] vector) {
         double result = variance(vector);
         result = Math.sqrt(result);
@@ -749,8 +755,8 @@ public final class Mathematics {
      */
     public static double product(double[] vals) {
         double prod = 1.;
-        for (int i = 0; i < vals.length; i++) {
-            prod *= vals[i];
+        for (double val : vals) {
+            prod *= val;
         }
         return prod;
     }

test/eva2/tools/math/MathematicsTest.java

@@ -0,0 +1,111 @@
+package eva2.tools.math;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class MathematicsTest {
+
+    @Test
+    public void testEuclidianDist() throws Exception {
+
+    }
+
+    @Test
+    public void testMax() throws Exception {
+        double[] vals = {1,2,3,4,5,6,4,3,2,2,12};
+        assertEquals(12.0, Mathematics.max(vals), 0.0);
+    }
+
+    @Test
+    public void testMean() throws Exception {
+        double[] vals = {2.0,3.05,4.9,7.8,12.7};
+        assertEquals(6.09, Mathematics.mean(vals), 0.0);
+    }
+
+    @Test
+    public void testZeroes() throws Exception {
+        double[] vals = Mathematics.zeroes(10);
+        for (final double val : vals) {
+            assertEquals(0.0, val, 0.0);
+        }
+    }
+
+    @Test
+    public void testContains() throws Exception {
+        assertTrue(Mathematics.contains(new int[]{1,2,3,4,5}, 4));
+    }
+
+    @Test
+    public void testMakeVector() throws Exception {
+        double[] vals = Mathematics.makeVector(42.23, 10);
+        assertEquals(10, vals.length);
+        for (final double val : vals) {
+            assertEquals(42.23, val, 0.0);
+        }
+    }
+
+    @Test
+    public void testMeanVect() throws Exception {
+
+    }
+
+    @Test
+    public void testMedian() throws Exception {
+
+    }
+
+    @Test
+    public void testMedian2() throws Exception {
+
+    }
+
+    @Test
+    public void testVariance() throws Exception {
+        double[] values = {9.8,9.2,12.3,15.7,3.14};
+
+        assertEquals(21.37892, Mathematics.variance(values), 0.000001);
+    }
+
+    @Test
+    public void testStdDev() throws Exception {
+        double[] values = {12.9,13.5,19.8,12.3,10.7};
+
+        // Mean
+        assertEquals(13.84, Mathematics.mean(values), 0.000001);
+        // Variance of sample
+        assertEquals(12.188, Mathematics.variance(values), 0.000001);
+        // Sample std.dev.
+        assertEquals(3.491131, Mathematics.stdDev(values), 0.000001);
+    }
+
+    @Test
+    public void testMin() throws Exception {
+        double[] values = {1.9,2.8,3.7,4.6,5.5};
+
+        assertEquals(1.9, Mathematics.min(values), 0.0);
+    }
+
+    @Test
+    public void testProjectToRange() throws Exception {
+
+    }
+
+    @Test
+    public void testScaleRange() throws Exception {
+
+    }
+
+    @Test
+    public void testSum() throws Exception {
+        double[] values = {1.9,2.8,3.7,4.6,5.5};
+
+        assertEquals(18.5, Mathematics.sum(values), 0.0);
+    }
+
+    @Test
+    public void testScale() throws Exception {
+
+    }
+}