umontreal.iro.lecuyer.randvar
Class NegativeBinomialGen

java.lang.Object
  umontreal.iro.lecuyer.randvar.RandomVariateGen
      umontreal.iro.lecuyer.randvar.RandomVariateGenInt
          umontreal.iro.lecuyer.randvar.NegativeBinomialGen

public class NegativeBinomialGen
extends RandomVariateGenInt

This class implements random variate generators having the negative binomial distribution. Its mass function is

p(x) = Γ(γ + x)/(x! Γ(γ)) p^γ(1 - p)^x, for x = 0, 1, 2,…

where Γ is the gamma function, γ > 0 and 0 <= p <= 1. No local copy of the parameters γ and p is maintained in this class. The (non-static) nextInt method simply calls inverseF on the distribution.

Constructor Summary

NegativeBinomialGen(RandomStream s, double gamma, double p)
Creates a negative binomial random variate generator with parameters γ = gamma and p, using stream s.

NegativeBinomialGen(RandomStream s, NegativeBinomialDist dist)
Creates a new generator for the distribution dist, using stream s.

Method Summary

double	getGamma() Returns the parameter γ of this object.
double	getP() Returns the parameter p of this object.
static int	nextInt(RandomStream s, double gamma, double p) Generates a new variate from the negative binomial distribution, with parameters γ = gamma and p = p, using stream s.

Methods inherited from class umontreal.iro.lecuyer.randvar.RandomVariateGenInt

getDistribution, nextArrayOfInt, nextInt

Methods inherited from class umontreal.iro.lecuyer.randvar.RandomVariateGen

getStream, nextArrayOfDouble, nextDouble, setStream, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

NegativeBinomialGen

public NegativeBinomialGen(RandomStream s,
                           double gamma,
                           double p)

Creates a negative binomial random variate generator with parameters γ = gamma and p, using stream s.

NegativeBinomialGen

public NegativeBinomialGen(RandomStream s,
                           NegativeBinomialDist dist)

Creates a new generator for the distribution dist, using stream s.

Method Detail

nextInt

public static int nextInt(RandomStream s,
                          double gamma,
                          double p)

Generates a new variate from the negative binomial distribution, with parameters γ = gamma and p = p, using stream s.

getGamma

public double getGamma()

Returns the parameter γ of this object.

getP

public double getP()

Returns the parameter p of this object.