accuracy score with test

src/Phpml/Metric/Accuracy.php

@@ -0,0 +1,39 @@
+<?php
+declare(strict_types = 1);
+
+namespace Phpml\Metric;
+
+use Phpml\Exception\InvalidArgumentException;
+
+class Accuracy
+{
+
+    /**
+     * @param array $actualLabels
+     * @param array $predictedLabels
+     * @param bool $normalize
+     *
+     * @return float|int
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function score(array $actualLabels, array $predictedLabels, bool $normalize = true)
+    {
+        if (count($actualLabels) != count($predictedLabels)) {
+            throw InvalidArgumentException::sizeNotMatch();
+        }
+
+        $score = 0;
+        foreach ($actualLabels as $index => $label) {
+            if($label===$predictedLabels[$index]) {
+                $score++;
+            }
+        }
+
+        if($normalize) {
+            $score = $score / count($actualLabels);
+        }
+
+        return $score;
+    }
+}

tests/Phpml/Metric/AccuracyTest.php

@@ -0,0 +1,38 @@
+<?php
+declare(strict_types = 1);
+
+namespace tests\Phpml\Metric;
+
+use Phpml\Metric\Accuracy;
+
+class AccuracyTest extends \PHPUnit_Framework_TestCase
+{
+
+    /**
+     * @expectedException \Phpml\Exception\InvalidArgumentException
+     */
+    public function testThrowExceptionOnInvalidArguments()
+    {
+        $actualLabels = ['a', 'b', 'a', 'b'];
+        $predictedLabels = ['a', 'a'];
+
+        Accuracy::score($actualLabels, $predictedLabels);
+    }
+
+    public function testCalculateNormalizedScore()
+    {
+        $actualLabels = ['a', 'b', 'a', 'b'];
+        $predictedLabels = ['a', 'a', 'b', 'b'];
+
+        $this->assertEquals(0.5, Accuracy::score($actualLabels, $predictedLabels));
+    }
+
+    public function testCalculateNotNormalizedScore()
+    {
+        $actualLabels = ['a', 'b', 'a', 'b'];
+        $predictedLabels = ['a', 'b', 'b', 'b'];
+
+        $this->assertEquals(3, Accuracy::score($actualLabels, $predictedLabels, false));
+    }
+
+}