change transformer behavior to reference

src/Phpml/FeatureExtraction/TfIdfTransformer.php

@@ -15,10 +15,8 @@ class TfIdfTransformer implements Transformer
 
     /**
      * @param array $samples
-     * 
-     * @return array
      */
-    public function transform(array $samples): array
+    public function transform(array &$samples)
     {
         $this->countTokensFrequency($samples);
 
@@ -32,8 +30,6 @@ class TfIdfTransformer implements Transformer
                 $feature = $feature * $this->idf[$index];
             }
         }
-
-        return $samples;
     }
 
     /**

src/Phpml/FeatureExtraction/TokenCountVectorizer.php

@@ -48,10 +48,8 @@ class TokenCountVectorizer implements Transformer
 
     /**
      * @param array $samples
-     *
-     * @return array
      */
-    public function transform(array $samples): array
+    public function transform(array &$samples)
     {
         $this->buildVocabulary($samples);
 
@@ -60,8 +58,6 @@ class TokenCountVectorizer implements Transformer
         }
 
         $samples = $this->checkDocumentFrequency($samples);
-
-        return $samples;
     }
 
     /**

src/Phpml/Pipeline.php

@@ -18,7 +18,7 @@ class Pipeline implements Estimator
 
     /**
      * @param array|Transformer[] $transformers
-     * @param Estimator $estimator
+     * @param Estimator           $estimator
      */
     public function __construct(array $transformers = [], Estimator $estimator)
     {
@@ -76,11 +76,11 @@ class Pipeline implements Estimator
 
     /**
      * @param array $samples
+     *
      * @return mixed
      */
     public function predict(array $samples)
     {
         return $this->estimator->predict($samples);
     }
-
 }

src/Phpml/Transformer.php

@@ -8,8 +8,6 @@ interface Transformer
 {
     /**
      * @param array $samples
-     *
-     * @return array
      */
-    public function transform(array $samples): array;
+    public function transform(array &$samples);
 }

tests/Phpml/FeatureExtraction/TfIdfTransformerTest.php

@@ -23,7 +23,8 @@ class TfIdfTransformerTest extends \PHPUnit_Framework_TestCase
         ];
 
         $transformer = new TfIdfTransformer();
+        $transformer->transform($samples);
 
-        $this->assertEquals($tfIdfSamples, $transformer->transform($samples), '', 0.001);
+        $this->assertEquals($tfIdfSamples, $samples, '', 0.001);
     }
 }

tests/Phpml/FeatureExtraction/TokenCountVectorizerTest.php

@@ -37,8 +37,9 @@ class TokenCountVectorizerTest extends \PHPUnit_Framework_TestCase
         ];
 
         $vectorizer = new TokenCountVectorizer(new WhitespaceTokenizer());
+        $vectorizer->transform($samples);
 
-        $this->assertEquals($tokensCounts, $vectorizer->transform($samples));
+        $this->assertEquals($tokensCounts, $samples);
         $this->assertEquals($vocabulary, $vectorizer->getVocabulary());
     }
 
@@ -68,8 +69,9 @@ class TokenCountVectorizerTest extends \PHPUnit_Framework_TestCase
         ];
 
         $vectorizer = new TokenCountVectorizer(new WhitespaceTokenizer(), 0.5);
+        $vectorizer->transform($samples);
 
-        $this->assertEquals($tokensCounts, $vectorizer->transform($samples));
+        $this->assertEquals($tokensCounts, $samples);
         $this->assertEquals($vocabulary, $vectorizer->getVocabulary());
 
         // word at least once in all samples
@@ -86,7 +88,8 @@ class TokenCountVectorizerTest extends \PHPUnit_Framework_TestCase
         ];
 
         $vectorizer = new TokenCountVectorizer(new WhitespaceTokenizer(), 1);
+        $vectorizer->transform($samples);
 
-        $this->assertEquals($tokensCounts, $vectorizer->transform($samples));
+        $this->assertEquals($tokensCounts, $samples);
     }
 }

tests/Phpml/PipelineTest.php

@@ -10,11 +10,10 @@ use Phpml\Pipeline;
 
 class PipelineTest extends \PHPUnit_Framework_TestCase
 {
-
     public function testPipelineConstruction()
     {
         $transformers = [
-            new TfIdfTransformer()
+            new TfIdfTransformer(),
         ];
         $estimator = new SVC();
 
@@ -23,5 +22,4 @@ class PipelineTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($transformers, $pipeline->getTransformers());
         $this->assertEquals($estimator, $pipeline->getEstimator());
     }
-
 }