org.apache.commons.math.distribution
Class BinomialDistributionImpl

java.lang.Object
  org.apache.commons.math.distribution.AbstractDistribution
      org.apache.commons.math.distribution.AbstractIntegerDistribution
          org.apache.commons.math.distribution.BinomialDistributionImpl

All Implemented Interfaces:

BinomialDistribution, DiscreteDistribution, Distribution, IntegerDistribution, Serializable

public class BinomialDistributionImpl

extends AbstractIntegerDistribution

implements BinomialDistribution, Serializable

The default implementation of BinomialDistribution.

Version:

$Revision: 1.19 $ $Date: 2004/11/07 03:32:48 $

See Also:

Serialized Form

Field Summary

(package private) static long

serialVersionUID Serializable version identifier

Constructor Summary

BinomialDistributionImpl(int trials, double p)
Create a binomial distribution with the given number of trials and probability of success.

Method Summary

double	cumulativeProbability(int x) For this distribution, X, this method returns P(X ≤ x).
protected int	getDomainLowerBound(double p) Access the domain value lower bound, based on p, used to bracket a PDF root.
protected int	getDomainUpperBound(double p) Access the domain value upper bound, based on p, used to bracket a PDF root.
int	getNumberOfTrials() Access the number of trials for this distribution.
double	getProbabilityOfSuccess() Access the probability of success for this distribution.
int	inverseCumulativeProbability(double p) For this distribution, X, this method returns the largest x, such that P(X ≤ x) ≤ p.
double	probability(int x) For this disbution, X, this method returns P(X = x).
void	setNumberOfTrials(int trials) Change the number of trials for this distribution.
void	setProbabilityOfSuccess(double p) Change the probability of success for this distribution.

Methods inherited from class org.apache.commons.math.distribution.AbstractIntegerDistribution

cumulativeProbability, cumulativeProbability, probability

Methods inherited from class org.apache.commons.math.distribution.AbstractDistribution

cumulativeProbability

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.commons.math.distribution.IntegerDistribution

cumulativeProbability

Methods inherited from interface org.apache.commons.math.distribution.DiscreteDistribution

probability

Methods inherited from interface org.apache.commons.math.distribution.Distribution

cumulativeProbability, cumulativeProbability

Field Detail

serialVersionUID

static final long serialVersionUID

Serializable version identifier

See Also:

Constant Field Values

Constructor Detail

BinomialDistributionImpl

public BinomialDistributionImpl(int trials,
                                double p)

Create a binomial distribution with the given number of trials and probability of success.

Parameters:

trials - the number of trials.

p - the probability of success.

Method Detail

getNumberOfTrials

public int getNumberOfTrials()

Access the number of trials for this distribution.

Specified by:

getNumberOfTrials in interface BinomialDistribution

Returns:

the number of trials.

getProbabilityOfSuccess

public double getProbabilityOfSuccess()

Access the probability of success for this distribution.

Specified by:

getProbabilityOfSuccess in interface BinomialDistribution

Returns:

the probability of success.

setNumberOfTrials

public void setNumberOfTrials(int trials)

Change the number of trials for this distribution.

Specified by:

setNumberOfTrials in interface BinomialDistribution

Parameters:

trials - the new number of trials.

Throws:

IllegalArgumentException - if trials is not a valid number of trials.

setProbabilityOfSuccess

public void setProbabilityOfSuccess(double p)

Change the probability of success for this distribution.

Specified by:

setProbabilityOfSuccess in interface BinomialDistribution

Parameters:

p - the new probability of success.

Throws:

IllegalArgumentException - if p is not a valid probability.

getDomainLowerBound

protected int getDomainLowerBound(double p)

Access the domain value lower bound, based on p, used to bracket a PDF root.

Specified by:

getDomainLowerBound in class AbstractIntegerDistribution

Parameters:

p - the desired probability for the critical value

Returns:

domain value lower bound, i.e. P(X < lower bound) < p

getDomainUpperBound

protected int getDomainUpperBound(double p)

Access the domain value upper bound, based on p, used to bracket a PDF root.

Specified by:

getDomainUpperBound in class AbstractIntegerDistribution

Parameters:

p - the desired probability for the critical value

Returns:

domain value upper bound, i.e. P(X < upper bound) > p

cumulativeProbability

public double cumulativeProbability(int x)
                             throws MathException

For this distribution, X, this method returns P(X ≤ x).

Specified by:

cumulativeProbability in interface IntegerDistribution

Specified by:

cumulativeProbability in class AbstractIntegerDistribution

Parameters:

x - the value at which the PDF is evaluated.

Returns:

PDF for this distribution.

Throws:

MathException - if the cumulative probability can not be computed due to convergence or other numerical errors.

probability

public double probability(int x)

For this disbution, X, this method returns P(X = x).

Specified by:

probability in interface IntegerDistribution

Parameters:

x - the value at which the PMF is evaluated.

Returns:

PMF for this distribution.

inverseCumulativeProbability

public int inverseCumulativeProbability(double p)
                                 throws MathException

For this distribution, X, this method returns the largest x, such that P(X ≤ x) ≤ p.

Returns -1 for p=0 and Integer.MAX_VALUE for p=1.

Specified by:

inverseCumulativeProbability in interface IntegerDistribution

Overrides:

inverseCumulativeProbability in class AbstractIntegerDistribution

Parameters:

p - the desired probability

Returns:

the largest x such that P(X ≤ x) <= p

Throws:

MathException - if the inverse cumulative probability can not be computed due to convergence or other numerical errors.

IllegalArgumentException - if p < 0 or p > 1