Class PoissonSlow

java.lang.Object
cern.colt.PersistentObject
cern.jet.random.AbstractDistribution
cern.jet.random.AbstractDiscreteDistribution
cern.jet.random.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
See Also:

  • Field Details

    • mean

      protected double mean

    • cached_sq

      protected double cached_sq

    • cached_alxm

      protected double cached_alxm

    • cached_g

      protected double cached_g

    • MEAN_MAX

      protected static final double MEAN_MAX
      See Also:

    • SWITCH_MEAN

      protected static final double SWITCH_MEAN
      See Also:

    • cof

      protected static final double[] cof

    • shared

      protected static PoissonSlow shared

  • Constructor Details

    • PoissonSlow

      public PoissonSlow(double mean, RandomEngine randomGenerator)
      Constructs a poisson distribution. Example: mean=1.0.

  • Method Details

    • 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 invalid input: '<' xx invalid input: '<' 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

    • nextInt

      private int nextInt(double theMean)
      Returns a random number from the distribution; bypasses the internal state.

    • nextIntSlow

      protected int nextIntSlow()
      Returns a random number from the distribution.

    • 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

    • xstaticSetRandomGenerator

      private static void xstaticSetRandomGenerator(RandomEngine randomGenerator)
      Sets the uniform random number generated shared by all static methods.
      Parameters:
      randomGenerator - the new uniform random number generator to be shared.