Gamma Distribution

Name

UxHwDoubleGammaDist, UxHwFloatGammaDist — Create a Gamma distribution.

Synopsis

#include <uxhw.h>

double	UxHwDoubleGammaDist(double k, double theta);
float	UxHwFloatGammaDist(float k, float theta);

Description

The UxHwDoubleGammaDist() function, on architectures that associate distributional information with floating-point values, creates a Gamma distribution with parameters k and theta and associates it with its return value. The particle return value is the mean value of an Gamma distribution with parameters k and theta. The probability density function of the Gamma distribution is

$$\begin{cases} \frac{1}{\Gamma(k)\theta^k}x^{k-1}e^{-x/\theta} & x>0, \\ 0 & x \le 0. \end{cases}$$

Parameters

• k — The shape parameter ($k$) of the Gamma distribution.
• theta — The scale parameter ($\theta$) of the Gamma distribution.

Return Values

The UxHwDoubleGammaDist() function returns the mean of samples of a Gamma distribution with parameter k. If k <= 0, the function returns NaN. If theta < 0, the function returns NaN. If theta = 0, the function returns 0.

✏️   Examples

#include <stdio.h>
#include <uxhw.h>

int
main(void)
{
	double	value = UxHwDoubleGammaDist(1.0,3.0);
	printf("value = %lf\n", value);

	return 0;
}