Chi-squared Distribution

Name

UxHwDoubleChiSquaredDist, UxHwFloatChiSquaredDist — Create an $\chi^2$ distribution.

Synopsis

#include <uxhw.h>

double	UxHwDoubleChiSquaredDist(double k);
float	UxHwFloatChiSquaredDist(float k);

Description

The UxHwDoubleChiSquaredDist() function, on architectures that associate distributional information with floating-point values, creates a $\chi^2$ distribution with parameter k and associates it with its return value. The particle return value is the mean value of a $\chi^2$ distribution with parameter k. The probability density function of the $\chi^2$ distribution is

$$\begin{cases} \frac{1}{\Gamma(k/2)2^k}x^{k/2-1}e^{-x/2} & x\ge 0, \\ 0 & x < 0. \end{cases}$$

Parameters

• k $\in (0, \infty)$ — The parameter ($k$) of the $\chi^2$ distribution.

Return values

The UxHwDoubleChiSquaredDist() function returns the mean value of a $\chi^2$ distribution with parameter k and associates it with a $\chi^2$ distribution with parameter k.

Illegal parameter values

If k <= 0, the function returns NaN. If k is NaN, the function returns -NaN. See Handling of NaN.

Examples

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

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

  return 0;
}