MDL-58859 mlbackend_php: Added to core

Part of MDL-57791 epic.
2017-07-24 07:51:54 +02:00
parent 229ae617c5
commit 9e84757bf0
129 changed files with 11485 additions and 0 deletions
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpml\CrossValidation;
+
+use Phpml\Dataset\ArrayDataset;
+use Phpml\Dataset\Dataset;
+
+class StratifiedRandomSplit extends RandomSplit
+{
+    /**
+     * @param Dataset $dataset
+     * @param float   $testSize
+     */
+    protected function splitDataset(Dataset $dataset, float $testSize)
+    {
+        $datasets = $this->splitByTarget($dataset);
+
+        foreach ($datasets as $targetSet) {
+            parent::splitDataset($targetSet, $testSize);
+        }
+    }
+
+    /**
+     * @param Dataset $dataset
+     *
+     * @return Dataset[]|array
+     */
+    private function splitByTarget(Dataset $dataset): array
+    {
+        $targets = $dataset->getTargets();
+        $samples = $dataset->getSamples();
+
+        $uniqueTargets = array_unique($targets);
+        $split = array_combine($uniqueTargets, array_fill(0, count($uniqueTargets), []));
+
+        foreach ($samples as $key => $sample) {
+            $split[$targets[$key]][] = $sample;
+        }
+
+        $datasets = $this->createDatasets($uniqueTargets, $split);
+
+        return $datasets;
+    }
+
+    /**
+     * @param array $uniqueTargets
+     * @param array $split
+     *
+     * @return array
+     */
+    private function createDatasets(array $uniqueTargets, array $split): array
+    {
+        $datasets = [];
+        foreach ($uniqueTargets as $target) {
+            $datasets[$target] = new ArrayDataset($split[$target], array_fill(0, count($split[$target]), $target));
+        }
+
+        return $datasets;
+    }
+}