mirror of
https://github.com/Llewellynvdm/php-ml.git
synced 2025-04-08 19:21:52 +00:00
46fa2c2cca
* update ECS config to v4 * composer: require Symplify 4 * apply coding-standard: use constants over functions, protected setUp() in tests, array indentation * ecs: add false positive case * composer: update lock * bump to ECS 4.4 * update composer.lock * shorten ECS config name * ecs: ignore assignments in while() * fix cs
51 lines
1.1 KiB
PHP
51 lines
1.1 KiB
PHP
<?php
|
|
|
|
declare(strict_types=1);
|
|
|
|
namespace Phpml\Math\Statistic;
|
|
|
|
class Gaussian
|
|
{
|
|
/**
|
|
* @var float
|
|
*/
|
|
protected $mean;
|
|
|
|
/**
|
|
* @var float
|
|
*/
|
|
protected $std;
|
|
|
|
public function __construct(float $mean, float $std)
|
|
{
|
|
$this->mean = $mean;
|
|
$this->std = $std;
|
|
}
|
|
|
|
/**
|
|
* Returns probability density of the given <i>$value</i>
|
|
*
|
|
* @return float|int
|
|
*/
|
|
public function pdf(float $value)
|
|
{
|
|
// Calculate the probability density by use of normal/Gaussian distribution
|
|
// Ref: https://en.wikipedia.org/wiki/Normal_distribution
|
|
$std2 = $this->std ** 2;
|
|
$mean = $this->mean;
|
|
|
|
return exp(-(($value - $mean) ** 2) / (2 * $std2)) / sqrt(2 * $std2 * M_PI);
|
|
}
|
|
|
|
/**
|
|
* Returns probability density value of the given <i>$value</i> based on
|
|
* given standard deviation and the mean
|
|
*/
|
|
public static function distributionPdf(float $mean, float $std, float $value): float
|
|
{
|
|
$normal = new self($mean, $std);
|
|
|
|
return $normal->pdf($value);
|
|
}
|
|
}
|