edu.stanford.nlp.sequences
Class FactoredSequenceModel

java.lang.Object
  edu.stanford.nlp.sequences.FactoredSequenceModel

All Implemented Interfaces:

SequenceModel

public class FactoredSequenceModel
extends java.lang.Object
implements SequenceModel

Author:

grenager Date: Dec 14, 2004 nmramesh Date: May 12, 2010

Constructor Summary

FactoredSequenceModel(SequenceModel[] models, double[] weights)

FactoredSequenceModel(SequenceModel model1, SequenceModel model2)

FactoredSequenceModel(SequenceModel model1, SequenceModel model2, double wt1, double wt2)
using this constructor results in a weighted addition of the two models' scores.

Method Summary

int[]	getPossibleValues(int position) 0...leftWindow-1 etc are null, leftWindow...length+leftWindow-1 are words, length+leftWindow...length+leftWindow+rightWindow-1 are null;
int	leftWindow() How many positions to the left a position is dependent on.
int	length()
int	rightWindow() How many positions to the right a position is dependent on.
double	scoreOf(int[] sequence) Computes the score assigned by this model to the provided sequence.
double	scoreOf(int[] sequence, int pos) Computes the unnormalized log conditional distribution over values of the element at position pos in the sequence, conditioned on the values of the elements in all other positions of the provided sequence.
double[]	scoresOf(int[] sequence, int pos) Computes the distribution over values of the element at position pos in the sequence, conditioned on the values of the elements in all other positions of the provided sequence.

Methods inherited from class java.lang.Object

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

Constructor Detail

FactoredSequenceModel

public FactoredSequenceModel(SequenceModel model1,
                             SequenceModel model2,
                             double wt1,
                             double wt2)

using this constructor results in a weighted addition of the two models' scores.

Parameters:

model1 -

model2 -

wt1 - weight of model1

wt2 - weight of model2

FactoredSequenceModel

public FactoredSequenceModel(SequenceModel model1,
                             SequenceModel model2)

FactoredSequenceModel

public FactoredSequenceModel(SequenceModel[] models,
                             double[] weights)

Method Detail

scoresOf

public double[] scoresOf(int[] sequence,
                         int pos)

Computes the distribution over values of the element at position pos in the sequence, conditioned on the values of the elements in all other positions of the provided sequence.

Specified by:

scoresOf in interface SequenceModel

Parameters:

sequence - the sequence containing the rest of the values to condition on

pos - the position of the element to give a distribution for

Returns:

an array of type double, representing a probability distribution; must sum to 1.0

scoreOf

public double scoreOf(int[] sequence,
                      int pos)

Description copied from interface: SequenceModel

Computes the unnormalized log conditional distribution over values of the element at position pos in the sequence, conditioned on the values of the elements in all other positions of the provided sequence.

Specified by:

scoreOf in interface SequenceModel

Parameters:

sequence - the sequence containing the rest of the values to condition on

pos - the position of the element to give a distribution for

Returns:

the log score of the token at the specified position in the sequence

scoreOf

public double scoreOf(int[] sequence)

Computes the score assigned by this model to the provided sequence. Typically this will be a probability in log space (since the probabilities are small).

Specified by:

scoreOf in interface SequenceModel

Parameters:

sequence - the sequence to compute a score for

Returns:

the score for the sequence

length

public int length()

Specified by:

length in interface SequenceModel

Returns:

the length of the sequence

leftWindow

public int leftWindow()

Description copied from interface: SequenceModel

How many positions to the left a position is dependent on.

Specified by:

leftWindow in interface SequenceModel

Returns:

the size of the left window used by this sequence model

rightWindow

public int rightWindow()

Description copied from interface: SequenceModel

How many positions to the right a position is dependent on.

Specified by:

rightWindow in interface SequenceModel

Returns:

the size of the right window used by this sequence model

getPossibleValues

public int[] getPossibleValues(int position)

Description copied from interface: SequenceModel

0...leftWindow-1 etc are null, leftWindow...length+leftWindow-1 are words, length+leftWindow...length+leftWindow+rightWindow-1 are null;

Specified by:

getPossibleValues in interface SequenceModel

Parameters:

position - the position

Returns:

the set of possible int values at this position, as an int array