Package org.uncommons.maths.random
Class BinomialGenerator
java.lang.Object
org.uncommons.maths.random.BinomialGenerator
- All Implemented Interfaces:
NumberGenerator<Integer>
Discrete random sequence that follows a
binomial
distribution.
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Field Summary
Fields -
Constructor Summary
ConstructorsConstructorDescriptionBinomialGenerator
(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
Modifier and TypeMethodDescriptionprivate int
binomialWithEvenProbability
(int n) Generating binomial values when p = 0.5 is straightforward.Generate the next binomial value from the current values of n and p.
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Field Details
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rng
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n
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p
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pBits
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lastP
private transient double lastP
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Constructor Details
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BinomialGenerator
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
NumberGenerator
s. 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
- ANumberGenerator
that provides the number of trials for the Binomial distribution used for the next generated value. This generator must produce only positive values.p
- ANumberGenerator
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.
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BinomialGenerator
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.
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Method Details
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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 interfaceNumberGenerator<Integer>
- Returns:
- The next value from the generator.
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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.
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