Gamcdf

Description

Computes the lower/upper tail probability for the gamma distribution with real degrees of freedom, with parameters a and b.

Syntax

double prob = gamcdf(double g, double a, double b[, int tail])

Parameters

g

Input, the value of the gamma variate.

a

Input, the shape parameter $\alpha$ of the gamma distribution, must be positive($a>0$).

b

Input, the scale parameter $\beta$ of the gamma distribution, must be positive($b>0$).

tail

Input, Optional. The tail probability type using for the gamma distribution
• 1 = the for upper tail probability
• 2 = the lower tail probability (Default if not set)

prob

Output, the returned probability.

Example

gamcdf(150,2,2,1)=; //ANS: 2.0357640909741E-31