Calculate standard deviation

standard-deviation.php

<?php

/**
 * Calculate standard deviation
 *
 * Square root of sum of squares divided by N-1
 *
 * @param list<float> $values
 */
function sd(array $values): float
{
    $noOfValues = count($values);
    $sum = array_sum(
        array_map(
            static function (float $x, float $mean): float {
                return pow($x - $mean, 2);
            },
            $values,
            array_fill(0, $noOfValues, array_sum($values) / $noOfValues)
        )
    );

    return sqrt($sum / ($noOfValues - 1));
}

echo sd([67, 89, 93, 102, 84]), "\n";