F.php
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<?php
namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;
use PhpOffice\PhpSpreadsheet\Calculation\Exception;
use PhpOffice\PhpSpreadsheet\Calculation\Functions;
class F
{
/**
* F.DIST.
*
* Returns the F probability distribution.
* You can use this function to determine whether two data sets have different degrees of diversity.
* For example, you can examine the test scores of men and women entering high school, and determine
* if the variability in the females is different from that found in the males.
*
* @param mixed $value Float value for which we want the probability
* @param mixed $u The numerator degrees of freedom as an integer
* @param mixed $v The denominator degrees of freedom as an integer
* @param mixed $cumulative Boolean value indicating if we want the cdf (true) or the pdf (false)
*
* @return float|string
*/
public static function distribution($value, $u, $v, $cumulative)
{
$value = Functions::flattenSingleValue($value);
$u = Functions::flattenSingleValue($u);
$v = Functions::flattenSingleValue($v);
$cumulative = Functions::flattenSingleValue($cumulative);
try {
$value = DistributionValidations::validateFloat($value);
$u = DistributionValidations::validateInt($u);
$v = DistributionValidations::validateInt($v);
$cumulative = DistributionValidations::validateBool($cumulative);
} catch (Exception $e) {
return $e->getMessage();
}
if ($value < 0 || $u < 1 || $v < 1) {
return Functions::NAN();
}
if ($cumulative) {
$adjustedValue = ($u * $value) / ($u * $value + $v);
return Beta::incompleteBeta($adjustedValue, $u / 2, $v / 2);
}
return (Gamma::gammaValue(($v + $u) / 2) /
(Gamma::gammaValue($u / 2) * Gamma::gammaValue($v / 2))) *
(($u / $v) ** ($u / 2)) *
(($value ** (($u - 2) / 2)) / ((1 + ($u / $v) * $value) ** (($u + $v) / 2)));
}
}