# tablepress/3.4/libraries/vendor/PhpSpreadsheet/Calculation/Statistical/Distributions/Poisson.php

TablePress – Tables in WordPress made easy, version 3.4. 67 lines.

- Page: https://pluginprobe.com/plugins/tablepress/3.4/code/libraries/vendor/PhpSpreadsheet/Calculation/Statistical/Distributions/Poisson.php
- Raw: https://pluginprobe.com/plugins/tablepress/3.4/raw/libraries/vendor/PhpSpreadsheet/Calculation/Statistical/Distributions/Poisson.php
- Modified: 2025-08-26T04:06:14+00:00

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```php
<?php

namespace TablePress\PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;

use TablePress\PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
use TablePress\PhpOffice\PhpSpreadsheet\Calculation\Exception;
use TablePress\PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
use TablePress\PhpOffice\PhpSpreadsheet\Calculation\MathTrig;

class Poisson
{
	use ArrayEnabled;

	/**
	 * POISSON.
	 *
	 * Returns the Poisson distribution. A common application of the Poisson distribution
	 * is predicting the number of events over a specific time, such as the number of
	 * cars arriving at a toll plaza in 1 minute.
	 *
	 * @param mixed $value Float value for which we want the probability
	 *                      Or can be an array of values
	 * @param mixed $mean Mean value as a float
	 *                      Or can be an array of values
	 * @param mixed $cumulative Boolean value indicating if we want the cdf (true) or the pdf (false)
	 *                      Or can be an array of values
	 *
	 * @return array<mixed>|float|string The result, or a string containing an error
	 *         If an array of numbers is passed as an argument, then the returned result will also be an array
	 *            with the same dimensions
	 */
	public static function distribution($value, $mean, $cumulative)
	{
		if (is_array($value) || is_array($mean) || is_array($cumulative)) {
			return self::evaluateArrayArguments([self::class, __FUNCTION__], $value, $mean, $cumulative);
		}

		try {
			$value = DistributionValidations::validateFloat($value);
			$mean = DistributionValidations::validateFloat($mean);
			$cumulative = DistributionValidations::validateBool($cumulative);
		} catch (Exception $e) {
			return $e->getMessage();
		}

		if (($value < 0) || ($mean < 0)) {
			return ExcelError::NAN();
		}

		if ($cumulative) {
			$summer = 0;
			$floor = floor($value);
			for ($i = 0; $i <= $floor; ++$i) {
				/** @var float $fact */
				$fact = MathTrig\Factorial::fact($i);
				$summer += $mean ** $i / $fact;
			}

			return exp(0 - $mean) * $summer;
		}
		/** @var float $fact */
		$fact = MathTrig\Factorial::fact($value);

		return (exp(0 - $mean) * $mean ** $value) / $fact;
	}
}

```