Poisson
cern.jet.random

Class Poisson

  • All Implemented Interfaces:
    DoubleFunction, IntFunction, Serializable, Cloneable


    public class Poissonextends AbstractDiscreteDistribution
    Poisson distribution (quick); 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: High performance implementation. Patchwork Rejection/Inversion method.

    This is a port of pprsc.c from the C-RAND / WIN-RAND library. C-RAND's implementation, in turn, is based upon

    H. Zechner (1994): Efficient sampling from continuous and discrete unimodal distributions, Doctoral Dissertation, 156 pp., Technical University Graz, Austria.

    Also see

    Stadlober E., H. Zechner (1999), The patchwork rejection method for sampling from unimodal distributions, to appear in ACM Transactions on Modelling and Simulation.

    See Also:
    Serialized Form
    • Constructor Detail

      • Poisson

        public Poisson(double mean,       RandomEngine randomGenerator)
        Constructs a poisson distribution. Example: mean=1.0.
    • Method Detail

      • cdf

        public double cdf(int k)
        Returns the cumulative distribution function.
      • clone

        public Object clone()
        Returns a deep copy of the receiver; the copy will produce identical sequences. After this call has returned, the copy and the receiver have equal but separate state.
        Overrides:
        clone in class AbstractDistribution
        Returns:
        a copy of the receiver.
      • nextInt

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

        public double pdf(int k)
        Returns the probability distribution function.
      • 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

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