z-Scores(standard deviation and mean) in PHP

Question

I am trying to calculate Z-scores using PHP. Essentially, I am looking for the most efficient way to calculate the mean and standard deviation of a data set (PHP array). Any

Answer 1

This is the same std dev code from the php pages mentioned in the top answer, but modernized a bit, without the one-line array magic and separate helper function:

/**
 * Calculates the standard deviation of an array of numbers.
 * @param   array   $array  The array of numbers to calculate the standard deviation of.
 * @return  float   The standard deviation of the numbers in the given array.
 */
function calculateStdDev(array $array): float
{
    $size = count($array);
    $mean = array_sum($array) / $size;
    $squares = array_map(function ($x) use ($mean) {
        return pow($x - $mean, 2);
    }, $array);

    return sqrt(array_sum($squares) / ($size - 1));
}