com.aliasi.stats

Class MultivariateDistribution

java.lang.Object

com.aliasi.stats.AbstractDiscreteDistribution

com.aliasi.stats.MultivariateDistribution

All Implemented Interfaces:

DiscreteDistribution

Direct Known Subclasses:

BernoulliDistribution, MultivariateConstant, MultivariateDistributionTest.Distro, MultivariateEstimator

public abstract class MultivariateDistribution
extends AbstractDiscreteDistribution

A MultivariateDistribution implements a discrete distribution over a finite set of outcomes numbered consecutively from zero. The total number of outcomes is given by the abstract method numDimensions(). The minimum outcome is zero and the maximum outcome is the number of dimensions minus one. Concrete subclasses must also implement the method probability(long).

Outcomes in multivariate distributions are labeled by strings. The method label(long) returns the label for an outcome. The inverse method outcome(String) maps labels to outcomes. The default implementation in this class provides labels defined by converting the long integer outcomes to strings. Subclasses may override these methods (together) to implement a more meaningful notion of label.

Note that the multivariate distribution forms the basis of the mulitnomial distribution. The Bernoulli distribution is a special case of the multivariate distribution with two outcomes.

For more information, see:

• Eric W. Weisstein. Multivariate Distribution. From MathWorld--A Wolfram Web Resource.

Since:

LingPipe2.0

Version:

2.0

Author:

Bob Carpenter

Constructor Summary

Constructors

Constructor and Description
MultivariateDistribution() Construct a multivariate distribution.

Method Summary

Methods

Modifier and Type	Method and Description
String	label(long outcome) Return the label for the specified outcome.
double	log2Probability(String label) Returns the log (base 2) probability of the outcome specified by label.
long	maxOutcome() Returns the maximum outcome with non-zero probability for a multivariate distribution.
long	minOutcome() Returns zero, the minimum outcome with non-zero probability for a multivariate distribution.
abstract int	numDimensions() Returns the number of dimensions of this multivariate distribution.
long	outcome(String label) Return the outcome for the specified label.
abstract double	probability(long outcome) Return the probability of the specified outcome in this multivariate distribution.
double	probability(String label) Returns the probability of the outcome specified by label.

Methods inherited from class com.aliasi.stats.AbstractDiscreteDistribution

cumulativeProbability, cumulativeProbabilityGreater, cumulativeProbabilityLess, entropy, log2Probability, mean, variance

Methods inherited from class java.lang.Object

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

Constructor Detail

MultivariateDistribution

public MultivariateDistribution()

Construct a multivariate distribution.

Method Detail

minOutcome

public long minOutcome()

Returns zero, the minimum outcome with non-zero probability for a multivariate distribution.

Specified by:

minOutcome in interface DiscreteDistribution

Overrides:

minOutcome in class AbstractDiscreteDistribution

Returns:

Zero.

maxOutcome

public long maxOutcome()

Returns the maximum outcome with non-zero probability for a multivariate distribution. This method returns the number of dimensions as specified by numDimensions() minus one.

Specified by:

maxOutcome in interface DiscreteDistribution

Overrides:

maxOutcome in class AbstractDiscreteDistribution

Returns:

The maximum outcome with non-zero probability for this distribution.

outcome

public long outcome(String label)

Return the outcome for the specified label. The default implementation is to return the result of applying the method Long.parseLong(String) to the specified label. If the label is not a number, -1 is returned.

Parameters:

label - Label whose outcome is returned.

Returns:

The outcome for the specified label.

label

public String label(long outcome)

Return the label for the specified outcome. The default implementation in this class is to return the result of Long.toString(long) applied to the outcome.

Parameters:

outcome - Outcome whose label is returned.

Returns:

The label for the specified outcome.

Throws:

IllegalArgumentException - If the outcome index is out of range.

probability

public double probability(String label)

Returns the probability of the outcome specified by label. If there is no known outcome with the specified label, this method will return 0.0.

Parameters:

label - Label of outcome.

Returns:

The probability of the outcome specified by label.

log2Probability

public double log2Probability(String label)

Returns the log (base 2) probability of the outcome specified by label. If there is no known outcome with the specified label, this method will return Double.NEGATIVE_INFINITY.

Parameters:

label - Label of outcome.

Returns:

The log probability of the outcome specified by label.

numDimensions

public abstract int numDimensions()

Returns the number of dimensions of this multivariate distribution. Note that this must be a positive number.

Returns:

The number of dimensions for this distribution.

probability

public abstract double probability(long outcome)

Return the probability of the specified outcome in this multivariate distribution.

Specified by:

probability in interface DiscreteDistribution

Specified by:

probability in class AbstractDiscreteDistribution

Parameters:

outcome - Outcome whose probability is returned.

Returns:

The probability of the specified outcome.