Phpml\Math\Statistic\StandardDeviation::population()

Complexity

Conditions	6
Paths	6

Size

Total Lines	25
Code Lines	14

Duplication

Lines	0
Ratio	0 %

Importance

Changes	2
Bugs	0	Features	1

<?php
    public static function population(array $a, $sample = true)
    {
        if (empty($a)) {
            throw InvalidArgumentException::arrayCantBeEmpty();
        }

        $n = count($a);

        if ($sample && $n === 1) {
            throw InvalidArgumentException::arraySizeToSmall(2);
        }

        $mean = Mean::arithmetic($a);
        $carry = 0.0;
        foreach ($a as $val) {
            $d = $val - $mean;
            $carry += $d * $d;
        };

        if ($sample) {
            --$n;
        }

        return sqrt($carry / $n);
    }
}