Check if feature exist when predict target in NaiveBayes (#327)

* Check if feature exist when predict target in NaiveBayes

* Fix typo

Author: akondas

src/Classification/NaiveBayes.php

@@ -4,6 +4,7 @@
 
 namespace Phpml\Classification;
 
+use Phpml\Exception\InvalidArgumentException;
 use Phpml\Helper\Predictable;
 use Phpml\Helper\Trainable;
 use Phpml\Math\Statistic\Mean;
@@ -137,6 +138,10 @@ private function calculateStatistics(string $label, array $samples): void
      */
     private function sampleProbability(array $sample, int $feature, string $label): float
     {
+        if (!isset($sample[$feature])) {
+            throw new InvalidArgumentException('Missing feature. All samples must have equal number of features');
+        }
+
         $value = $sample[$feature];
         if ($this->dataType[$label][$feature] == self::NOMINAL) {
             if (!isset($this->discreteProb[$label][$feature][$value]) ||

tests/Classification/NaiveBayesTest.php

@@ -5,6 +5,7 @@
 namespace Phpml\Tests\Classification;
 
 use Phpml\Classification\NaiveBayes;
+use Phpml\Exception\InvalidArgumentException;
 use Phpml\ModelManager;
 use PHPUnit\Framework\TestCase;
 
@@ -125,4 +126,19 @@ public function testSaveAndRestoreNumericLabels(): void
         self::assertEquals($classifier, $restoredClassifier);
         self::assertEquals($predicted, $restoredClassifier->predict($testSamples));
     }
+
+    public function testInconsistentFeaturesInSamples(): void
+    {
+        $trainSamples = [[5, 1, 1], [1, 5, 1], [1, 1, 5]];
+        $trainLabels = ['1996', '1997', '1998'];
+
+        $testSamples = [[3, 1, 1], [5, 1], [4, 3, 8]];
+
+        $classifier = new NaiveBayes();
+        $classifier->train($trainSamples, $trainLabels);
+
+        $this->expectException(InvalidArgumentException::class);
+
+        $classifier->predict($testSamples);
+    }
 }