Package org.evoludo.math

Class RNGDistribution.Binomial

Object

RNGDistribution

Binomial

Enclosing class:

RNGDistribution

public static class RNGDistribution.Binomial
extends RNGDistribution

Binomially distributed random numbers with support {0,1,2,3,..., n}. This represents the number of successes in n trials each with a probability of success p.

See Also:

• Wikipedia: Binomial distribution

Nested Class Summary

Nested classes/interfaces inherited from class RNGDistribution

RNGDistribution.Binomial, RNGDistribution.Exponential, RNGDistribution.Geometric, RNGDistribution.Gillespie, RNGDistribution.Normal, RNGDistribution.TestCommand, RNGDistribution.Uniform

Field Summary

Fields

Modifier and Type	Field	Description
private double[]	cdf	Cumulative distribution function of binomial probability distribution.
private double	mean	Mean number of successes n p.
private double	p	Success probability of single trial.

Fields inherited from class RNGDistribution

rng, seed, seedSet, testSamples

Constructor Summary

Constructors

Constructor	Description
Binomial(double p, int n)	Creates binomial distribution with n trials and success probability p (mean n p) and a new instance of MersenneTwister..
Binomial(MersenneTwister rng, double p, int n)	Creates binomial distribution with n trials and success probability p (mean n p) and the random number generator rng.

Method Summary

Modifier and Type	Method	Description
RNGDistribution.Binomial	clone()	Clone this RNGDistribution to ensure both objects return identical sequences of random numbers.
double	getProbability()	Get the probability of success p of a single trial for the binomial distribution.
int	getTrials()	Get the number of trials n for the binomial distribution.
int	next()	Generate the number of successful trials drawn from the binomial distribution.
static int	next(MersenneTwister rng, double p, int n)	Creates binomial distribution for n trials with success probability p (mean n p) and the random number generator rng.
void	setProbabilityTrials(double p, int n)	Set the probability of success p and the number of trials n.
static void	test(MersenneTwister rng, Logger logger, MersenneTwister.Chronometer clock)	Test Binomial distribution.

Methods inherited from class RNGDistribution

clearRNGSeed, clone, getRNG, getRNGSeed, isRNGSeedSet, nextBoolean, nextByte, nextBytes, nextDouble, nextGaussian, nextInt, nextInt, random01, random01d, random0n, random0N, setRNG, setRNGSeed, setRNGSeed

Methods inherited from class Object

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

Field Details

cdf

private double[] cdf

Cumulative distribution function of binomial probability distribution.

p

private double p

Success probability of single trial.

mean

private double mean

Mean number of successes n p.

Constructor Details

Binomial

public Binomial(double p,
 int n)

Creates binomial distribution with n trials and success probability p (mean n p) and a new instance of MersenneTwister..

Parameters:

p - success probability of single trial

n - number of trials

Binomial

public Binomial(MersenneTwister rng,
 double p,
 int n)
         throws IllegalArgumentException

Creates binomial distribution with n trials and success probability p (mean n p) and the random number generator rng.

Parameters:

rng - random number generator

p - success probability of single trial

n - number of trials

Throws:

IllegalArgumentException

Method Details

setProbabilityTrials

public void setProbabilityTrials(double p,
 int n)
                          throws IllegalArgumentException

Set the probability of success p and the number of trials n. This calculates the cumulative probabilities for the binomial distribution.

Parameters:

p - probability of success of single trial

n - number of trials

Throws:

IllegalArgumentException - if p≤0, p≥1 or n<0

getProbability

public double getProbability()

Get the probability of success p of a single trial for the binomial distribution.

Returns:

the success probability of a single trial

getTrials

public int getTrials()

Get the number of trials n for the binomial distribution.

Returns:

the number of trials

next

public int next()

Generate the number of successful trials drawn from the binomial distribution.

Returns:

the number of successful trials

clone

public RNGDistribution.Binomial clone()

Description copied from class: RNGDistribution

Clone this RNGDistribution to ensure both objects return identical sequences of random numbers.

IMPORTANT:

1. overrides clone() in Object but conflicts with GWT's aversion to clone()ing...
2. remove @SuppressWarnings("all") to ensure that no other issues crept in when modifying method.

Specified by:

clone in class RNGDistribution

Returns:

clone of RNGDistribution

next

public static int next(MersenneTwister rng,
 double p,
 int n)

Creates binomial distribution for n trials with success probability p (mean n p) and the random number generator rng.

Note: cumulative distribution function is generated on the fly. This is fine if only a few binomially distributed random numbers are required or if performance is of a minor concern. Otherwise use Binomial(double, int)} and next().

Parameters:

rng - random number generator

p - probability of success of single trial

n - number of trials

Returns:

number of successful trials

test

public static void test(MersenneTwister rng,
 Logger logger,
 MersenneTwister.Chronometer clock)

Test Binomial distribution.

The test samples the distribution and bins the random numbers. This sample distribution is compared to the theoretical expectation. The mean deviation is the mean difference between the actual number of events in each bin and their expected number. For a perfect match the mean deviation is 0. The test passes if the mean deviation lies within one standard error from 0. This is more stringent than the traditional 95% confidence interval.

Parameters:

rng - the random number generator

logger - the logger for reporting results

clock - the stop watch