diff --git a/src/Phpml/FeatureExtraction/TokenCountVectorizer.php b/src/Phpml/FeatureExtraction/TokenCountVectorizer.php
index 14fc69c..cde5278 100644
--- a/src/Phpml/FeatureExtraction/TokenCountVectorizer.php
+++ b/src/Phpml/FeatureExtraction/TokenCountVectorizer.php
@@ -23,6 +23,11 @@ class TokenCountVectorizer implements Vectorizer
      */
     private $vocabulary;
 
+    /**
+     * @var array
+     */
+    private $tokens;
+
     /**
      * @var array
      */
@@ -47,8 +52,10 @@ class TokenCountVectorizer implements Vectorizer
      */
     public function transform(array $samples): array
     {
+        $this->buildVocabulary($samples);
+
         foreach ($samples as $index => $sample) {
-            $samples[$index] = $this->transformSample($sample);
+            $samples[$index] = $this->transformSample($index);
         }
 
         $samples = $this->checkDocumentFrequency($samples);
@@ -65,14 +72,29 @@ class TokenCountVectorizer implements Vectorizer
     }
 
     /**
-     * @param string $sample
+     * @param array $samples
+     */
+    private function buildVocabulary(array &$samples)
+    {
+        foreach ($samples as $index => $sample) {
+            $tokens = $this->tokenizer->tokenize($sample);
+            foreach ($tokens as $token) {
+                $this->addTokenToVocabulary($token);
+            }
+            $this->tokens[$index] = $tokens;
+        }
+    }
+
+    /**
+     * @param int $index
      *
      * @return array
      */
-    private function transformSample(string $sample)
+    private function transformSample(int $index)
     {
         $counts = [];
-        $tokens = $this->tokenizer->tokenize($sample);
+        $tokens = $this->tokens[$index];
+
         foreach ($tokens as $token) {
             $index = $this->getTokenIndex($token);
             $this->updateFrequency($token);
@@ -83,21 +105,33 @@ class TokenCountVectorizer implements Vectorizer
             ++$counts[$index];
         }
 
+        foreach ($this->vocabulary as $index) {
+            if (!isset($counts[$index])) {
+                $counts[$index] = 0;
+            }
+        }
+
         return $counts;
     }
 
     /**
      * @param string $token
      *
-     * @return mixed
+     * @return int
      */
-    private function getTokenIndex(string $token)
+    private function getTokenIndex(string $token): int
+    {
+        return $this->vocabulary[$token];
+    }
+
+    /**
+     * @param string $token
+     */
+    private function addTokenToVocabulary(string $token)
     {
         if (!isset($this->vocabulary[$token])) {
             $this->vocabulary[$token] = count($this->vocabulary);
         }
-
-        return $this->vocabulary[$token];
     }
 
     /**
@@ -122,7 +156,7 @@ class TokenCountVectorizer implements Vectorizer
         if ($this->minDF > 0) {
             $beyondMinimum = $this->getBeyondMinimumIndexes(count($samples));
             foreach ($samples as $index => $sample) {
-                $samples[$index] = $this->unsetBeyondMinimum($sample, $beyondMinimum);
+                $samples[$index] = $this->resetBeyondMinimum($sample, $beyondMinimum);
             }
         }
 
@@ -135,10 +169,10 @@ class TokenCountVectorizer implements Vectorizer
      *
      * @return array
      */
-    private function unsetBeyondMinimum(array $sample, array $beyondMinimum)
+    private function resetBeyondMinimum(array $sample, array $beyondMinimum)
     {
         foreach ($beyondMinimum as $index) {
-            unset($sample[$index]);
+            $sample[$index] = 0;
         }
 
         return $sample;
diff --git a/tests/Phpml/FeatureExtraction/TokenCountVectorizerTest.php b/tests/Phpml/FeatureExtraction/TokenCountVectorizerTest.php
index 64ac569..5166575 100644
--- a/tests/Phpml/FeatureExtraction/TokenCountVectorizerTest.php
+++ b/tests/Phpml/FeatureExtraction/TokenCountVectorizerTest.php
@@ -17,16 +17,28 @@ class TokenCountVectorizerTest extends \PHPUnit_Framework_TestCase
             'Mauris diam eros fringilla diam',
         ];
 
-        $vocabulary = ['Lorem', 'ipsum', 'dolor', 'sit', 'amet', 'Mauris', 'placerat', 'diam', 'eros', 'fringilla'];
-        $vector = [
-            [0 => 1, 1 => 1, 2 => 2, 3 => 1, 4 => 1],
-            [5 => 1, 6 => 1, 1 => 1, 2 => 1],
-            [5 => 1, 7 => 2, 8 => 1, 9 => 1],
+        $vocabulary = [
+            0 => 'Lorem',
+            1 => 'ipsum',
+            2 => 'dolor',
+            3 => 'sit',
+            4 => 'amet',
+            5 => 'Mauris',
+            6 => 'placerat',
+            7 => 'diam',
+            8 => 'eros',
+            9 => 'fringilla',
+        ];
+
+        $tokensCounts = [
+            [0 => 1, 1 => 1, 2 => 2, 3 => 1, 4 => 1, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0],
+            [0 => 0, 1 => 1, 2 => 1, 3 => 0, 4 => 0, 5 => 1, 6 => 1, 7 => 0, 8 => 0, 9 => 0],
+            [0 => 0, 1 => 0, 2 => 0, 3 => 0, 4 => 0, 5 => 1, 6 => 0, 7 => 2, 8 => 1, 9 => 1],
         ];
 
         $vectorizer = new TokenCountVectorizer(new WhitespaceTokenizer());
 
-        $this->assertEquals($vector, $vectorizer->transform($samples));
+        $this->assertEquals($tokensCounts, $vectorizer->transform($samples));
         $this->assertEquals($vocabulary, $vectorizer->getVocabulary());
     }
 
@@ -40,34 +52,41 @@ class TokenCountVectorizerTest extends \PHPUnit_Framework_TestCase
             'ipsum sit amet',
         ];
 
-        $vocabulary = ['Lorem', 'ipsum', 'dolor', 'sit', 'amet'];
-        $vector = [
-            [0 => 1, 1 => 1, 3 => 1, 4 => 1],
-            [0 => 1, 1 => 1, 3 => 1, 4 => 1],
-            [1 => 1, 3 => 1, 4 => 1],
-            [1 => 1, 3 => 1, 4 => 1],
+        $vocabulary = [
+            0 => 'Lorem',
+            1 => 'ipsum',
+            2 => 'dolor',
+            3 => 'sit',
+            4 => 'amet',
+        ];
+
+        $tokensCounts = [
+            [0 => 1, 1 => 1, 2 => 0, 3 => 1, 4 => 1],
+            [0 => 1, 1 => 1, 2 => 0, 3 => 1, 4 => 1],
+            [0 => 0, 1 => 1, 2 => 0, 3 => 1, 4 => 1],
+            [0 => 0, 1 => 1, 2 => 0, 3 => 1, 4 => 1],
         ];
 
         $vectorizer = new TokenCountVectorizer(new WhitespaceTokenizer(), 0.5);
 
-        $this->assertEquals($vector, $vectorizer->transform($samples));
+        $this->assertEquals($tokensCounts, $vectorizer->transform($samples));
         $this->assertEquals($vocabulary, $vectorizer->getVocabulary());
 
-        // word at least in all samples
+        // word at least once in all samples
         $samples = [
             'Lorem ipsum dolor sit amet',
-            'Morbi quis lacinia arcu. Sed eu sagittis Lorem',
-            'Suspendisse gravida consequat eros Lorem',
+            'Morbi quis sagittis Lorem',
+            'eros Lorem',
         ];
 
-        $vector = [
-            [0 => 1],
-            [0 => 1],
-            [0 => 1],
+        $tokensCounts = [
+            [0 => 1, 1 => 0, 2 => 0, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0],
+            [0 => 1, 1 => 0, 2 => 0, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0],
+            [0 => 1, 1 => 0, 2 => 0, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0],
         ];
 
         $vectorizer = new TokenCountVectorizer(new WhitespaceTokenizer(), 1);
 
-        $this->assertEquals($vector, $vectorizer->transform($samples));
+        $this->assertEquals($tokensCounts, $vectorizer->transform($samples));
     }
 }
diff --git a/tests/Phpml/Metric/AccuracyTest.php b/tests/Phpml/Metric/AccuracyTest.php
index 1e71fcf..6f28d94 100644
--- a/tests/Phpml/Metric/AccuracyTest.php
+++ b/tests/Phpml/Metric/AccuracyTest.php
@@ -52,5 +52,4 @@ class AccuracyTest extends \PHPUnit_Framework_TestCase
 
         $this->assertEquals(0.959, $accuracy, '', 0.01);
     }
-
 }