add more standard deviation tests

2 files changed, 3 insertions, 29 deletions

diff --git a/lib/Entropy/Entropy.php b/lib/Entropy/Entropy.php
index 798db8b..9f4f038 100644
--- a/lib/Entropy/Entropy.php
+++ b/lib/Entropy/Entropy.php
@@ -61,33 +61,6 @@ class Entropy
         return sqrt((1 / $n) * $sum - pow($mean, 2));
     }
 
-    /**
-     * Calculates the standard deviation.
-     *
-     * @param array $array
-     *
-     * @return float
-     */
-    public function sd($array)
-    {
-        if (is_array($array) && count($array) > 0) {
-            // square root of sum of squares devided by N-1
-            return sqrt(array_sum(array_map(
-                function ($x, $mean) {
-                    return pow($x - $mean, 2);
-                },
-                $array,
-                array_fill(
-                    0,
-                    count($array),
-                (array_sum($array) / count($array))
-                )
-            )) / (count($array) - 1));
-        }
-
-        return 0.0;
-    }
-
     public function streamMean($oldMean, $value, $step) {
         $mean = 0;
         if ($step === 1) {
diff --git a/tests/Unit/Entropy/EntropyTest.php b/tests/Unit/Entropy/EntropyTest.php
index c4f515d..2e74ecf 100644
--- a/tests/Unit/Entropy/EntropyTest.php
+++ b/tests/Unit/Entropy/EntropyTest.php
@@ -63,7 +63,9 @@ class EntropyTest extends TestCase
     public function dataSd()
     {
         $tests = [];
-        $tests[] = [[10, 2, 38, 23, 38, 23, 21], 13.284434];
+        $tests[] = [[10, 2, 38, 23, 38, 23, 21], 12.298996];
+        $tests[] = [[10, 12, 23, 23, 16, 23, 21, 16], 4.898979]
+        $tests[] = [[-5, 1, 8, 7, 2], 4.673328]
 
         return $tests;
     }
@@ -76,7 +78,6 @@ class EntropyTest extends TestCase
      */
     public function testSd($data, $sd)
     {
-        $this->assertEquals(number_format($this->invokePrivate($this->entropy, 'sd', [$data]), 6), $sd);
         $sum = 0.0;
         $mean = 0.0;
         $standardDeviation = 0.0;