org.uncommons.maths.random
Class BinomialGenerator

java.lang.Object
  org.uncommons.maths.random.BinomialGenerator

All Implemented Interfaces:

NumberGenerator<Integer>

public class BinomialGenerator
extends Object
implements NumberGenerator<Integer>

Discrete random sequence that follows a binomial distribution.

Author:

Daniel Dyer

Constructor Summary

BinomialGenerator(int n, double p, Random rng)
Creates a generator of binomially-distributed values from a distribution with the specified parameters.

BinomialGenerator(NumberGenerator<Integer> n, NumberGenerator<Double> p, Random rng)
Creates a generator of binomially-distributed values.

Method Summary

Integer

nextValue() Generate the next binomial value from the current values of n and p.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BinomialGenerator

public BinomialGenerator(NumberGenerator<Integer> n,
                         NumberGenerator<Double> p,
                         Random rng)

Creates a generator of binomially-distributed values. The number of trials (n) and the probability of success in each trial (p) are determined by the provided NumberGenerators. This means that the statistical parameters of this generator may change over time. One example of where this is useful is if the n and p generators are attached to GUI controls that allow a user to tweak the parameters while a program is running.

To create a Binomial generator with a constant n and p, use the BinomialGenerator(int, double, Random) constructor instead.

Parameters:

n - A NumberGenerator that provides the number of trials for the Binomial distribution used for the next generated value. This generator must produce only positive values.

p - A NumberGenerator that provides the probability of succes in a single trial for the Binomial distribution used for the next generated value. This generator must produce only values in the range 0 - 1.

rng - The source of randomness.

BinomialGenerator

public BinomialGenerator(int n,
                         double p,
                         Random rng)

Creates a generator of binomially-distributed values from a distribution with the specified parameters.

Parameters:

n - The number of trials (and therefore the maximum possible value returned by this sequence).

p - The probability (between 0 and 1) of success in any one trial.

rng - The source of randomness used to generate the binomial values.

Method Detail

nextValue

public Integer nextValue()

Generate the next binomial value from the current values of n and p. The algorithm used is from The Art of Computer Programming Volume 2 (Seminumerical Algorithms) by Donald Knuth (page 589 in the Third Edition) where it is credited to J.H. Ahrens.

Specified by:

nextValue in interface NumberGenerator<Integer>

Returns:

The next value from the generator.