Prevent Division by zero error in classification report

src/Phpml/Metric/ClassificationReport.php

@@ -113,6 +113,10 @@ class ClassificationReport
     {
         foreach (['precision', 'recall', 'f1score'] as $metric) {
             $values = array_filter($this->$metric);
+            if(0==count($values)) {
+                $this->average[$metric] = 0.0;
+                continue;
+            }
             $this->average[$metric] = array_sum($values) / count($values);
         }
     }

tests/Phpml/Metric/ClassificationReportTest.php

@@ -67,4 +67,19 @@ class ClassificationReportTest extends  \PHPUnit_Framework_TestCase
 
         $this->assertEquals([1 => 0.0, 2 => 1, 3 => 0], $report->getPrecision(), '', 0.01);
     }
+
+    public function testPreventDividedByZeroWhenPredictedLabelsAllNotMatch()
+    {
+        $labels = [1,2,3,4,5];
+        $predicted = [2,3,4,5,6];
+
+        $report = new ClassificationReport($labels, $predicted);
+
+        $this->assertEquals([
+            'precision' => 0,
+            'recall' => 0,
+            'f1score' => 0
+        ], $report->getAverage(), '', 0.01);
+    }
+
 }