cern.jet.random.tdouble
Class PoissonSlow

java.lang.Object
  cern.colt.PersistentObject
      cern.jet.random.tdouble.AbstractDoubleDistribution
          cern.jet.random.tdouble.AbstractDiscreteDistribution
              cern.jet.random.tdouble.PoissonSlow

All Implemented Interfaces:

DoubleFunction, IntFunction, Serializable, Cloneable

public class PoissonSlow
extends AbstractDiscreteDistribution

Poisson distribution; See the math definition and animated definition.

p(k) = (mean^k / k!) * exp(-mean) for k >= 0.

Valid parameter ranges: mean > 0. Note: if mean <= 0.0 then always returns zero.

Instance methods operate on a user supplied uniform random number generator; they are unsynchronized.

Static methods operate on a default uniform random number generator; they are synchronized.

Implementation: This is a port of RandPoisson used in CLHEP 1.4.0 (C++). CLHEP's implementation, in turn, is based upon "W.H.Press et al., Numerical Recipes in C, Second Edition".

Version:

1.0, 09/24/99

Author:

wolfgang.hoschek@cern.ch

See Also:

Serialized Form

Constructor Summary

PoissonSlow(double mean, DoubleRandomEngine randomGenerator)
Constructs a poisson distribution.

Method Summary

static double	logGamma(double xx) Returns the value ln(Gamma(xx) for xx > 0.
int	nextInt() Returns a random number from the distribution.
void	setMean(double mean) Sets the mean.
static int	staticNextInt(double mean) Returns a random number from the distribution with the given mean.
String	toString() Returns a String representation of the receiver.

Methods inherited from class cern.jet.random.tdouble.AbstractDiscreteDistribution

nextDouble

Methods inherited from class cern.jet.random.tdouble.AbstractDoubleDistribution

apply, apply, clone, makeDefaultGenerator

Methods inherited from class java.lang.Object

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

Constructor Detail

PoissonSlow

public PoissonSlow(double mean,
                   DoubleRandomEngine randomGenerator)

Constructs a poisson distribution. Example: mean=1.0.

Method Detail

logGamma

public static double logGamma(double xx)

Returns the value ln(Gamma(xx) for xx > 0. Full accuracy is obtained for xx > 1. For 0 < xx < 1. the reflection formula (6.1.4) can be used first. (Adapted from Numerical Recipes in C)

nextInt

public int nextInt()

Returns a random number from the distribution.

Specified by:

nextInt in class AbstractDiscreteDistribution

setMean

public void setMean(double mean)

Sets the mean.

staticNextInt

public static int staticNextInt(double mean)

Returns a random number from the distribution with the given mean.

toString

public String toString()

Returns a String representation of the receiver.

Overrides:

toString in class Object