stats_rand_gen_normal

(PECL stats >= 1.0.0)

stats_rand_gen_normal — Generates a single random deviate from a normal distribution

説明

stats_rand_gen_normal(float $av, float $sd): float

Returns a random deviate from the normal distribution with mean, av, and standard deviation, sd.

パラメータ

av: The mean of the normal distribution
sd: The standard deviation of the normal distribution

戻り値

A random deviate

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User Contributed Notes 1 note

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KEINOS ¶

4 years ago

Alternative of "stats_rand_gen_normal()".

<?php
/**
 * "Box–Muller transform" based random deviate generator.
 *
 * @ref https://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform
 * 
 * @param  float|int $av Average/Mean
 * @param  float|int $sd Standard deviation
 * @return float
 */
if (! function_exists('stats_rand_gen_normal')) {
    function stats_rand_gen_normal($av, $sd): float
    {
        $x = mt_rand() / mt_getrandmax();
        $y = mt_rand() / mt_getrandmax();
    
        return sqrt(-2 * log($x)) * cos(2 * pi() * $y) * $sd + $av;
    }
}
?>

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