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Fix division by zero in ClassificationReport #21
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@ -37,7 +37,7 @@ class ClassificationReport
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*/
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public function __construct(array $actualLabels, array $predictedLabels)
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{
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$truePositive = $falsePositive = $falseNegative = $this->support = self::getLabelIndexedArray($actualLabels);
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$truePositive = $falsePositive = $falseNegative = $this->support = self::getLabelIndexedArray($actualLabels, $predictedLabels);
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foreach ($actualLabels as $index => $actual) {
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$predicted = $predictedLabels[$index];
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@ -103,8 +103,8 @@ class ClassificationReport
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private function computeMetrics(array $truePositive, array $falsePositive, array $falseNegative)
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{
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foreach ($truePositive as $label => $tp) {
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$this->precision[$label] = $tp / ($tp + $falsePositive[$label]);
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$this->recall[$label] = $tp / ($tp + $falseNegative[$label]);
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$this->precision[$label] = $this->computePrecision($tp, $falsePositive[$label]);
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$this->recall[$label] = $this->computeRecall($tp, $falseNegative[$label]);
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$this->f1score[$label] = $this->computeF1Score((float) $this->precision[$label], (float) $this->recall[$label]);
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}
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}
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@ -117,6 +117,36 @@ class ClassificationReport
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}
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}
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/**
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* @param int $truePositive
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* @param int $falsePositive
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*
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* @return float|string
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*/
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private function computePrecision(int $truePositive, int $falsePositive)
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{
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if (0 == ($divider = $truePositive + $falsePositive)) {
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return 0.0;
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}
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return $truePositive / $divider;
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}
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/**
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* @param int $truePositive
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* @param int $falseNegative
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*
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* @return float|string
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*/
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private function computeRecall(int $truePositive, int $falseNegative)
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{
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if (0 == ($divider = $truePositive + $falseNegative)) {
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return 0.0;
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}
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return $truePositive / $divider;
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}
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/**
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* @param float $precision
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* @param float $recall
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@ -133,13 +163,14 @@ class ClassificationReport
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}
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/**
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* @param array $labels
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* @param array $actualLabels
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* @param array $predictedLabels
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*
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* @return array
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*/
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private static function getLabelIndexedArray(array $labels): array
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private static function getLabelIndexedArray(array $actualLabels, array $predictedLabels): array
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{
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$labels = array_values(array_unique($labels));
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$labels = array_values(array_unique(array_merge($actualLabels, $predictedLabels)));
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sort($labels);
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$labels = array_combine($labels, array_fill(0, count($labels), 0));
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@ -47,4 +47,24 @@ class ClassificationReportTest extends \PHPUnit_Framework_TestCase
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$this->assertEquals($support, $report->getSupport(), '', 0.01);
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$this->assertEquals($average, $report->getAverage(), '', 0.01);
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}
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public function testPreventDivideByZeroWhenTruePositiveAndFalsePositiveSumEqualsZero()
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{
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$labels = [1, 2];
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$predicted = [2, 2];
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$report = new ClassificationReport($labels, $predicted);
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$this->assertEquals([1 => 0.0, 2 => 0.5], $report->getPrecision(), '', 0.01);
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}
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public function testPreventDivideByZeroWhenTruePositiveAndFalseNegativeSumEqualsZero()
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{
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$labels = [2, 2, 1];
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$predicted = [2, 2, 3];
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$report = new ClassificationReport($labels, $predicted);
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$this->assertEquals([1 => 0.0, 2 => 1, 3 => 0], $report->getPrecision(), '', 0.01);
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}
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}
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