/* returns normal cumulated distribution function */
double normalcdf(double x, double m, double s){
double z = (x - m) / s;
if (z >= 0)
return 0.5 + 0.5 * gammacdf(z * z / 2, 0.5);
else
return 0.5 - 0.5 * gammacdf(z * z / 2, 0.5);
}
/* returns logarithmic normal cumulated distribution function */
double lognormalcdf(double x, double a, double b) {
double z = (log(x) - a) / b;
if (x == 0)
return 0;
if (z >= 0)
return 0.5 + 0.5 * gammacdf(z * z / 2, 0.5);
else
return 0.5 - 0.5 * gammacdf(z * z / 2, 0.5);
}
/* chi2cdf: chi-square cumulative distribution function.
* @x: the x-value for evaluation.
* @k: the number of degrees of freedom.
*/
double chi2cdf (double x, double k) {
/* return the value. */
return gammacdf (x, k / 2.0, 2.0);
}