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cern.jet.random
Class Binomial

java.lang.Object
  extended bycern.colt.PersistentObject
      extended bycern.jet.random.AbstractDistribution
          extended bycern.jet.random.AbstractDiscreteDistribution
              extended bycern.jet.random.Binomial
All Implemented Interfaces:
Cloneable, DoubleFunction, IntFunction, Serializable
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.

Version:
1.0, 09/24/99
See Also:
Serialized Form

Field Summary
 
Fields inherited from class cern.colt.PersistentObject
serialVersionUID
 
Constructor Summary
Binomial(int n, double p, RandomEngine randomGenerator)
          Constructs a binomial distribution.
 
Method Summary
 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.

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