be.ac.ulg.montefiore.run.jahmm.toolbox
Class KullbackLeiblerDistanceCalculator

java.lang.Object
  be.ac.ulg.montefiore.run.jahmm.toolbox.KullbackLeiblerDistanceCalculator

public class KullbackLeiblerDistanceCalculator
extends java.lang.Object

Computes the distance between HMMs.

The distance metric is similar to the Kullback-Leibler distance defined on distributions. More information can be found in A Probabilistic Distance Measure For HMMs by Rabiner and Juang (AT&T Technical Journal, vol. 64, Feb. 1985, pages 391-408).

This distance measure is not symetric: distance(hmm1, hmm2) is not necessary equal to distance(hmm2, hmm1). To get a symetric distance definition, compute (distance(hmm1, hmm2) + distance(hmm2, hmm1)) / 2.

Constructor Summary

KullbackLeiblerDistanceCalculator()

Method Summary

<O extends Observation> double	distance(Hmm<O> hmm1, Hmm<? super O> hmm2) Computes the Kullback-Leibler distance between two HMMs.
int	getNbSequences() Returns the number of sequences generated to estimate a distance.
int	getSequencesLength() Returns the length of sequences generated to estimate a distance.
void	setNbSequences(int nb) Sets the number of sequences generated to estimate a distance.
void	setSequencesLength(int length) Sets the length of sequences generated to estimate a distance.

Methods inherited from class java.lang.Object

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

Constructor Detail

KullbackLeiblerDistanceCalculator

public KullbackLeiblerDistanceCalculator()

Method Detail

distance

public <O extends Observation> double distance(Hmm<O> hmm1,
                                               Hmm<? super O> hmm2)

Computes the Kullback-Leibler distance between two HMMs.

Parameters:

hmm1 - The first HMM against which the distance is computed. The distance is mesured with regard to this HMM (this must be defined since the Kullback-Leibler distance is not symetric).

hmm2 - The second HMM against which the distance is computed.

Returns:

The distance between hmm1 and hmm2 with regard to hmm1

getNbSequences

public int getNbSequences()

Returns the number of sequences generated to estimate a distance.

Returns:

The number of generated sequences.

setNbSequences

public void setNbSequences(int nb)

Sets the number of sequences generated to estimate a distance.

Parameters:

nb - The number of generated sequences.

getSequencesLength

public int getSequencesLength()

Returns the length of sequences generated to estimate a distance.

Returns:

The sequences length.

setSequencesLength

public void setSequencesLength(int length)

Sets the length of sequences generated to estimate a distance.

Parameters:

length - The sequences length.