Package org.apache.commons.math4.distribution

Class EnumeratedDistribution<T>

java.lang.Object

org.apache.commons.math4.distribution.EnumeratedDistribution<T>

Type Parameters:

T - type of the elements in the sample space.

All Implemented Interfaces:

java.io.Serializable

public class EnumeratedDistribution<T>
extends java.lang.Object
implements java.io.Serializable

A generic implementation of a discrete probability distribution (Wikipedia) over a finite sample space, based on an enumerated list of <value, probability> pairs. Input probabilities must all be non-negative, but zero values are allowed and their sum does not have to equal one. Constructors will normalize input probabilities to make them sum to one.

The list of <value, probability> pairs does not, strictly speaking, have to be a function and it can contain null values. The pmf created by the constructor will combine probabilities of equal values and will treat null values as equal. For example, if the list of pairs <"dog", 0.2>, <null, 0.1>, <"pig", 0.2>, <"dog", 0.1>, <null, 0.4> is provided to the constructor, the resulting pmf will assign mass of 0.5 to null, 0.3 to "dog" and 0.2 to null.

Since:

3.2

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	EnumeratedDistribution.Sampler	Sampler functionality.

Constructor Summary

Constructors

Constructor	Description
EnumeratedDistribution(java.util.List<Pair<T,java.lang.Double>> pmf)	Create an enumerated distribution using the given random number generator and probability mass function enumeration.

Method Summary

Modifier and Type	Method	Description
EnumeratedDistribution.Sampler	createSampler(UniformRandomProvider rng)	Creates a EnumeratedDistribution.Sampler.
java.util.List<Pair<T,java.lang.Double>>	getPmf()	Return the probability mass function as a list of <value, probability> pairs.

Methods inherited from class java.lang.Object

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

Constructor Details

EnumeratedDistribution

public EnumeratedDistribution(java.util.List<Pair<T,java.lang.Double>> pmf) throws NotPositiveException, MathArithmeticException, NotFiniteNumberException, NotANumberException

Create an enumerated distribution using the given random number generator and probability mass function enumeration.

Parameters:

pmf - probability mass function enumerated as a list of <T, probability> pairs.

Throws:

NotPositiveException - if any of the probabilities are negative.

NotFiniteNumberException - if any of the probabilities are infinite.

NotANumberException - if any of the probabilities are NaN.

MathArithmeticException - all of the probabilities are 0.

Method Details

getPmf

public java.util.List<Pair<T,java.lang.Double>> getPmf()

Return the probability mass function as a list of <value, probability> pairs.

Note that if duplicate and / or null values were provided to the constructor when creating this EnumeratedDistribution, the returned list will contain these values. If duplicates values exist, what is returned will not represent a pmf (i.e., it is up to the caller to consolidate duplicate mass points).

Returns:

the probability mass function.

createSampler

public EnumeratedDistribution.Sampler createSampler(UniformRandomProvider rng)

Creates a EnumeratedDistribution.Sampler.

Parameters:

rng - Random number generator.

Returns:

a new sampler instance.