org.encog.ml.hmm.alog

Class ForwardBackwardCalculator

java.lang.Object

org.encog.ml.hmm.alog.ForwardBackwardCalculator

Direct Known Subclasses:

ForwardBackwardScaledCalculator

public class ForwardBackwardCalculator
extends java.lang.Object

The forward-backward algorithm is an inference algorithm for hidden Markov models which computes the posterior marginals of all hidden state variables given a sequence of observations.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ForwardBackwardCalculator.Computation

Constructor Summary

Constructors

Constructor and Description
ForwardBackwardCalculator(MLDataSet oseq, HiddenMarkovModel hmm) Construct the forward/backward calculator.
ForwardBackwardCalculator(MLDataSet oseq, HiddenMarkovModel hmm, java.util.EnumSet<ForwardBackwardCalculator.Computation> flags) Construct the object.

Method Summary

Modifier and Type	Method and Description
double	alphaElement(int t, int i) Alpha element.
double	betaElement(int t, int i) Beta element, best element.
double	probability()

Methods inherited from class java.lang.Object

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

Constructor Detail

ForwardBackwardCalculator

public ForwardBackwardCalculator(MLDataSet oseq,
                                 HiddenMarkovModel hmm)

Construct the forward/backward calculator.

Parameters:

oseq - The sequence to use.

hmm - THe hidden markov model to use.

ForwardBackwardCalculator

public ForwardBackwardCalculator(MLDataSet oseq,
                                 HiddenMarkovModel hmm,
                                 java.util.EnumSet<ForwardBackwardCalculator.Computation> flags)

Construct the object.

Parameters:

oseq - The sequence.

hmm - The hidden markov model to use.

flags - Flags, alpha or beta.

Method Detail

alphaElement

public double alphaElement(int t,
                           int i)

Alpha element.

Parameters:

t - The row.

i - The column.

Returns:

The element.

betaElement

public double betaElement(int t,
                          int i)

Beta element, best element.

Parameters:

t - From.

i - To.

Returns:

The element.

probability

public double probability()

Returns:

The probability.