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46 lines
940 B
PHP
46 lines
940 B
PHP
<?php
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declare (strict_types = 1);
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namespace Phpml\Math\Statistic;
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use Phpml\Exception\InvalidArgumentException;
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class Correlation
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{
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/**
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* @param array|int[]|float[] $x
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* @param array|int[]|float[] $y
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*
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* @return float
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*
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* @throws InvalidArgumentException
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*/
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public static function pearson(array $x, array $y)
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{
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if (count($x) !== count($y)) {
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throw InvalidArgumentException::arraySizeNotMatch();
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}
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$count = count($x);
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$meanX = array_sum($x) / $count;
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$meanY = array_sum($y) / $count;
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$axb = 0;
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$a2 = 0;
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$b2 = 0;
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for ($i = 0;$i < $count;++$i) {
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$a = $x[$i] - $meanX;
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$b = $y[$i] - $meanY;
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$axb = $axb + ($a * $b);
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$a2 = $a2 + pow($a, 2);
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$b2 = $b2 + pow($b, 2);
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}
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$corr = $axb / sqrt($a2 * $b2);
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return $corr;
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}
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}
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