Colt 1.2.0

cern.jet.random
Class PoissonSlow

java.lang.Object
  extended bycern.colt.PersistentObject
      extended bycern.jet.random.AbstractDistribution
          extended bycern.jet.random.AbstractDiscreteDistribution
              extended bycern.jet.random.PoissonSlow
All Implemented Interfaces:
Cloneable, DoubleFunction, IntFunction, Serializable

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
See Also:
Serialized Form

Field Summary
 
Fields inherited from class cern.colt.PersistentObject
serialVersionUID
 
Constructor Summary
PoissonSlow(double mean, RandomEngine 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.AbstractDiscreteDistribution
nextDouble
 
Methods inherited from class cern.jet.random.AbstractDistribution
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,
                   RandomEngine 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.


Colt 1.2.0

Jump to the Colt Homepage