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.
  • Field Details

  • Constructor Details

    • 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 Details

    • 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.
    • binomialWithEvenProbability

      private int binomialWithEvenProbability(int n)
      Generating binomial values when p = 0.5 is straightforward. It simply a case of generating n random bits and counting how many are 1s.
      Parameters:
      n - The number of trials.
      Returns:
      The number of successful outcomes from n trials.