Gamma.php
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<?php
namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;
use PhpOffice\PhpSpreadsheet\Calculation\Exception;
use PhpOffice\PhpSpreadsheet\Calculation\Functions;
class Gamma extends GammaBase
{
/**
* GAMMA.
*
* Return the gamma function value.
*
* @param mixed $value Float value for which we want the probability
*
* @return float|string The result, or a string containing an error
*/
public static function gamma($value)
{
$value = Functions::flattenSingleValue($value);
try {
$value = DistributionValidations::validateFloat($value);
} catch (Exception $e) {
return $e->getMessage();
}
if ((((int) $value) == ((float) $value)) && $value <= 0.0) {
return Functions::NAN();
}
return self::gammaValue($value);
}
/**
* GAMMADIST.
*
* Returns the gamma distribution.
*
* @param mixed $value Float Value at which you want to evaluate the distribution
* @param mixed $a Parameter to the distribution as a float
* @param mixed $b Parameter to the distribution as a float
* @param mixed $cumulative Boolean value indicating if we want the cdf (true) or the pdf (false)
*
* @return float|string
*/
public static function distribution($value, $a, $b, $cumulative)
{
$value = Functions::flattenSingleValue($value);
$a = Functions::flattenSingleValue($a);
$b = Functions::flattenSingleValue($b);
try {
$value = DistributionValidations::validateFloat($value);
$a = DistributionValidations::validateFloat($a);
$b = DistributionValidations::validateFloat($b);
$cumulative = DistributionValidations::validateBool($cumulative);
} catch (Exception $e) {
return $e->getMessage();
}
if (($value < 0) || ($a <= 0) || ($b <= 0)) {
return Functions::NAN();
}
return self::calculateDistribution($value, $a, $b, $cumulative);
}
/**
* GAMMAINV.
*
* Returns the inverse of the Gamma distribution.
*
* @param mixed $probability Float probability at which you want to evaluate the distribution
* @param mixed $alpha Parameter to the distribution as a float
* @param mixed $beta Parameter to the distribution as a float
*
* @return float|string
*/
public static function inverse($probability, $alpha, $beta)
{
$probability = Functions::flattenSingleValue($probability);
$alpha = Functions::flattenSingleValue($alpha);
$beta = Functions::flattenSingleValue($beta);
try {
$probability = DistributionValidations::validateProbability($probability);
$alpha = DistributionValidations::validateFloat($alpha);
$beta = DistributionValidations::validateFloat($beta);
} catch (Exception $e) {
return $e->getMessage();
}
if (($alpha <= 0.0) || ($beta <= 0.0)) {
return Functions::NAN();
}
return self::calculateInverse($probability, $alpha, $beta);
}
/**
* GAMMALN.
*
* Returns the natural logarithm of the gamma function.
*
* @param mixed $value Float Value at which you want to evaluate the distribution
*
* @return float|string
*/
public static function ln($value)
{
$value = Functions::flattenSingleValue($value);
try {
$value = DistributionValidations::validateFloat($value);
} catch (Exception $e) {
return $e->getMessage();
}
if ($value <= 0) {
return Functions::NAN();
}
return log(self::gammaValue($value));
}
}