umontreal.iro.lecuyer.randvar
Class HypergeometricGen

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

public class HypergeometricGen
extends RandomVariateGenInt

This class implements random variate generators for the hypergeometric distribution. Its mass function is

p(x) = nCr(m, x)nCr(l - m, k - x)/nCr(l, k) for x = max(0, k - l + m),..., min(k, m)

where nCr(n, x) is the number of possible combinations when choosing x elements among a set of n elements, m, l and k are integers that satisfy 0 < m <= l and 0 < k <= l.

The generation method is inversion using the chop-down algorithm

Constructor Summary

HypergeometricGen(RandomStream s, HypergeometricDist dist)
Creates a new generator for distribution dist, using stream s.

HypergeometricGen(RandomStream s, int m, int l, int k)
Creates a hypergeometric generator with parameters m = m, l = l and k = k, using stream s.

Method Summary

int	getK() Returns the k associated with this object.
int	getL() Returns the l associated with this object.
int	getM() Returns the m associated with this object.
static int	nextInt(RandomStream s, int m, int l, int k) Generates a new variate from the hypergeometric distribution with parameters m = m, l = l and k = k, 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

HypergeometricGen

public HypergeometricGen(RandomStream s,
                         int m,
                         int l,
                         int k)

Creates a hypergeometric generator with parameters m = m, l = l and k = k, using stream s.

HypergeometricGen

public HypergeometricGen(RandomStream s,
                         HypergeometricDist dist)

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

Method Detail

nextInt

public static int nextInt(RandomStream s,
                          int m,
                          int l,
                          int k)

Generates a new variate from the hypergeometric distribution with parameters m = m, l = l and k = k, using stream s.

getM

public int getM()

Returns the m associated with this object.

getL

public int getL()

Returns the l associated with this object.

getK

public int getK()

Returns the k associated with this object.