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:

java.io.Serializable, BinomialDistribution, DiscreteDistribution, Distribution, IntegerDistribution

public class BinomialDistributionImpl
extends AbstractIntegerDistribution
implements BinomialDistribution, java.io.Serializable

The default implementation of BinomialDistribution.

See Also:

Serialized Form

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
double	cumulativeProbability(int x) For this distribution, X, this method returns P(X ≤ x).
int	getNumberOfTrials() Access the number of trials for this distribution.
double	getNumericalMean() Returns the mean.
double	getNumericalVariance() Returns the variance.
double	getProbabilityOfSuccess() Access the probability of success for this distribution.
int	getSupportLowerBound() Returns the lower bound of the support for the distribution.
int	getSupportUpperBound() Returns the upper bound of the support for the 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 distribution, X, this method returns P(X = x).
void	setNumberOfTrials(int trials) Deprecated. as of 2.1 (class will become immutable in 3.0)
void	setProbabilityOfSuccess(double p) Deprecated. as of 2.1 (class will become immutable in 3.0)

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

cumulativeProbability, cumulativeProbability, cumulativeProbability, isSupportLowerBoundInclusive, isSupportUpperBoundInclusive, probability, reseedRandomGenerator, sample, sample

Methods inherited from class java.lang.Object

equals, 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

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

@Deprecated
public void setNumberOfTrials(int trials)

Deprecated. as of 2.1 (class will become immutable in 3.0)

Change the number of trials for this distribution.

Specified by:

setNumberOfTrials in interface BinomialDistribution

Parameters:

trials - the new number of trials.

Throws:

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

setProbabilityOfSuccess

@Deprecated
public void setProbabilityOfSuccess(double p)

Deprecated. as of 2.1 (class will become immutable in 3.0)

Change the probability of success for this distribution.

Specified by:

setProbabilityOfSuccess in interface BinomialDistribution

Parameters:

p - the new probability of success.

Throws:

java.lang.IllegalArgumentException - if p is not a valid probability.

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 distribution, 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.

java.lang.IllegalArgumentException - if p < 0 or p > 1

getSupportLowerBound

public int getSupportLowerBound()

Returns the lower bound of the support for the distribution. The lower bound of the support is always 0 no matter the number of trials and probability parameter.

Returns:

lower bound of the support (always 0)

Since:

2.2

getSupportUpperBound

public int getSupportUpperBound()

Returns the upper bound of the support for the distribution. The upper bound of the support is the number of trials.

Returns:

upper bound of the support (equal to number of trials)

Since:

2.2

getNumericalMean

public double getNumericalMean()

Returns the mean. For n number of trials and probability parameter p, the mean is n * p

Returns:

the mean

Since:

2.2

getNumericalVariance

public double getNumericalVariance()

Returns the variance. For n number of trials and probability parameter p, the variance is n * p * (1 - p)

Returns:

the variance

Since:

2.2