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## cern.jet.random
Class PoissonSlow

    java.lang.Object
      cern.colt.PersistentObject
          cern.jet.random.AbstractDistribution
              cern.jet.random.AbstractDiscreteDistribution
                  cern.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.

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