Fix DecisionTreeRegressor for big dataset (#376)

README.md

@@ -79,6 +79,7 @@ Public datasets are available in a separate repository [php-ai/php-ml-datasets](
 * Regression
     * [Least Squares](http://php-ml.readthedocs.io/en/latest/machine-learning/regression/least-squares/)
     * [SVR](http://php-ml.readthedocs.io/en/latest/machine-learning/regression/svr/)
+    * DecisionTreeRegressor
 * Clustering
     * [k-Means](http://php-ml.readthedocs.io/en/latest/machine-learning/clustering/k-means/)
     * [DBSCAN](http://php-ml.readthedocs.io/en/latest/machine-learning/clustering/dbscan/)
@@ -87,6 +88,7 @@ Public datasets are available in a separate repository [php-ai/php-ml-datasets](
     * [Accuracy](http://php-ml.readthedocs.io/en/latest/machine-learning/metric/accuracy/)
     * [Confusion Matrix](http://php-ml.readthedocs.io/en/latest/machine-learning/metric/confusion-matrix/)
     * [Classification Report](http://php-ml.readthedocs.io/en/latest/machine-learning/metric/classification-report/)
+    * Regression
 * Workflow
     * [Pipeline](http://php-ml.readthedocs.io/en/latest/machine-learning/workflow/pipeline)
 * Neural Network

src/Regression/DecisionTreeRegressor.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Phpml\Regression;
 
+use Phpml\Exception\InvalidArgumentException;
 use Phpml\Exception\InvalidOperationException;
 use Phpml\Math\Statistic\Mean;
 use Phpml\Math\Statistic\Variance;
@@ -29,6 +30,27 @@ final class DecisionTreeRegressor extends CART implements Regression
      */
     protected $columns = [];
 
+    public function __construct(
+        int $maxDepth = PHP_INT_MAX,
+        int $maxLeafSize = 3,
+        float $minPurityIncrease = 0.,
+        ?int $maxFeatures = null,
+        float $tolerance = 1e-4
+    ) {
+        if ($maxFeatures !== null && $maxFeatures < 1) {
+            throw new InvalidArgumentException('Max features must be greater than 0');
+        }
+
+        if ($tolerance < 0.) {
+            throw new InvalidArgumentException('Tolerance must be equal or greater than 0');
+        }
+
+        $this->maxFeatures = $maxFeatures;
+        $this->tolerance = $tolerance;
+
+        parent::__construct($maxDepth, $maxLeafSize, $minPurityIncrease);
+    }
+
     public function train(array $samples, array $targets): void
     {
         $features = count($samples[0]);

src/Tree/CART.php

@@ -91,7 +91,7 @@ abstract class CART
 
             $depth++;
 
-            if ($left === [] || $right === []) {
+            if ($left[1] === [] || $right[1] === []) {
                 $node = $this->terminate(array_merge($left[1], $right[1]));
 
                 $current->attachLeft($node);

tests/Regression/DecisionTreeRegressorTest.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Phpml\Tests\Regression;
 
+use Phpml\Exception\InvalidArgumentException;
 use Phpml\Exception\InvalidOperationException;
 use Phpml\ModelManager;
 use Phpml\Regression\DecisionTreeRegressor;
@@ -45,6 +46,20 @@ class DecisionTreeRegressorTest extends TestCase
         $regression->predict([[1]]);
     }
 
+    public function testMaxFeaturesLowerThanOne(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new DecisionTreeRegressor(5, 3, 0.0, 0);
+    }
+
+    public function testToleranceSmallerThanZero(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new DecisionTreeRegressor(5, 3, 0.0, 20, -1);
+    }
+
     public function testSaveAndRestore(): void
     {
         $samples = [[60], [61], [62], [63], [65]];