public virtual double NextGamma(
	double a
)

Public Overridable Function NextGamma ( 
	a As Double
) As Double

public:
virtual double NextGamma(
	double a
)

abstract NextGamma : 
        a : float -> float 
override NextGamma : 
        a : float -> float 

Parameters

a

Type: SystemDouble
A double which specifies the shape parameter of the gamma distribution. It must be positive.

Return Value

Method NextGamma generates pseudorandom numbers from a gamma distribution with shape parameter a. The probability density function is

Various computational algorithms are used depending on the value of the shape parameter a. For the special case of a = 0.5, squared and halved normal deviates are used; and for the special case of a = 1.0, exponential deviates (from method NextExponential) are used. Otherwise, if a is less than 1.0, an acceptance-rejection method due to Ahrens, described in Ahrens and Dieter (1974), is used; if a is greater than 1.0, a ten-region rejection procedure developed by Schmeiser and Lal (1980) is used.

The Erlang distribution is a standard gamma distribution with the shape parameter having a value equal to a positive integer; hence, NextGamma generates pseudorandom deviates from an Erlang distribution with no modifications required.

Reference

Other Resources