Proyectos de Subversion Moodle

<?php

declare(strict_types=1);

namespace Phpml\Math\Statistic;

use Phpml\Exception\InvalidArgumentException;

class Correlation

{

    /**

     * @param int[]|float[] $x

     * @param int[]|float[] $y

     *

     * @throws InvalidArgumentException

     */

    public static function pearson(array $x, array $y): float

    {

        if (count($x) !== count($y)) {

            throw new InvalidArgumentException('Size of given arrays does not match');

        }

        $count = count($x);

        $meanX = Mean::arithmetic($x);

        $meanY = Mean::arithmetic($y);

        $axb = 0;

        $a2 = 0;

        $b2 = 0;

        for ($i = 0; $i < $count; ++$i) {

            $a = $x[$i] - $meanX;

            $b = $y[$i] - $meanY;

            $axb += ($a * $b);

            $a2 += $a ** 2;

            $b2 += $b ** 2;

        }

        return $axb / ($a2 * $b2) ** .5;

    }

}