cern.jet.random

Class Binomial

java.lang.Object

cern.colt.PersistentObject

cern.jet.random.AbstractDistribution

cern.jet.random.AbstractDiscreteDistribution

cern.jet.random.Binomial

All Implemented Interfaces:

DoubleFunction, IntFunction, Serializable, Cloneable

public class Binomial
extends AbstractDiscreteDistribution

Binomial distribution; See the math definition and animated definition.

p(x) = k * p^k * (1-p)^(n-k) with k = n! / (k! * (n-k)!).

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. Acceptance Rejection/Inversion method. This is a port of RandBinomial used in CLHEP 1.4.0 (C++). CLHEP's implementation is, in turn, based on

V. Kachitvichyanukul, B.W. Schmeiser (1988): Binomial random variate generation, Communications of the ACM 31, 216-222.

See Also:

Serialized Form

Field Summary

Fields inherited from class cern.colt.PersistentObject

serialVersionUID

Constructor Summary

Constructors

Constructor and Description
Binomial(int n, double p, RandomEngine randomGenerator) Constructs a binomial distribution.

Method Summary

Modifier and Type	Method and Description
double	cdf(int k) Returns the cumulative distribution function.
int	nextInt() Returns a random number from the distribution.
int	nextInt(int n, double p) Returns a random number from the distribution with the given parameters n and p; bypasses the internal state.
double	pdf(int k) Returns the probability distribution function.
void	setNandP(int n, double p) Sets the parameters number of trials and the probability of success.
static int	staticNextInt(int n, double p) Returns a random number from the distribution with the given parameters n and p.
String	toString() Returns a String representation of the receiver.

Methods inherited from class cern.jet.random.AbstractDiscreteDistribution

nextDouble

Methods inherited from class cern.jet.random.AbstractDistribution

apply, apply, clone, makeDefaultGenerator

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Binomial

public Binomial(int n,
                double p,
                RandomEngine randomGenerator)

Constructs a binomial distribution. Example: n=1, p=0.5.

Parameters:

n - the number of trials (also known as sample size).

p - the probability of success.

randomGenerator - a uniform random number generator.

Throws:

IllegalArgumentException - if n*Math.min(p,1-p) <= 0.0

Method Detail

cdf

public double cdf(int k)

Returns the cumulative distribution function.

nextInt

public int nextInt()

Returns a random number from the distribution.

Specified by:

nextInt in class AbstractDiscreteDistribution

nextInt

public int nextInt(int n,
                   double p)

Returns a random number from the distribution with the given parameters n and p; bypasses the internal state.

Parameters:

n - the number of trials

p - the probability of success.

Throws:

IllegalArgumentException - if n*Math.min(p,1-p) <= 0.0

pdf

public double pdf(int k)

Returns the probability distribution function.

setNandP

public void setNandP(int n,
                     double p)

Sets the parameters number of trials and the probability of success.

Parameters:

n - the number of trials

p - the probability of success.

Throws:

IllegalArgumentException - if n*Math.min(p,1-p) <= 0.0

staticNextInt

public static int staticNextInt(int n,
                                double p)

Returns a random number from the distribution with the given parameters n and p.

Parameters:

n - the number of trials

p - the probability of success.

Throws:

IllegalArgumentException - if n*Math.min(p,1-p) <= 0.0

toString

public String toString()

Returns a String representation of the receiver.

Overrides:

toString in class Object