uk.ac.gla.terrier.matching.models.languagemodel
Class PonteCroft

java.lang.Object
  uk.ac.gla.terrier.matching.models.languagemodel.LanguageModel
      uk.ac.gla.terrier.matching.models.languagemodel.PonteCroft

All Implemented Interfaces:

Model

public class PonteCroft
extends LanguageModel

This class implements Ponte & Croft's language modelling approach.

Version:

$Revision: 1.11 $

Author:

Ben He

Constructor Summary

PonteCroft()
The default constructor.

Method Summary

double	averageTermGenerationProbability(int[] tf, double[] docLength) The method computes the average term generation probability of a term in vocabulary.
java.lang.String	getInfo() Returns the name of the model.
double	risk(double tf, double docLength, double termEstimate) The method computes the risk of retrieving a seen query term.
double	scoreSeenNonQuery(double tf, double docLength, double termFrequency, double termEstimate) The method assigns score for a seen non-query term.
double	scoreSeenQuery(double tf, double docLength, double termFrequency, double termEstimate) The method assigns score for a seen query term.
double	scoreUnseenNonQuery(double termFrequency) The method assigns score for a unseen non-query term.
double	scoreUnseenQuery(double termFrequency) The method assigns score for a unseen query term.
void	setAverageDocumentLength(double a) Set the average document length in the collection.
void	setNumberOfPointers(double n)
void	setNumberOfTokens(double value) Set the number of tokens in the whole collection.
void	setNumberOfUniqueTerms(double n) Set the number of unique terms in the collection.

Methods inherited from class uk.ac.gla.terrier.matching.models.languagemodel.LanguageModel

getParameter, setNumberOfDocuments, setParameter, setTermFrequency

Methods inherited from class java.lang.Object

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

Constructor Detail

PonteCroft

public PonteCroft()

The default constructor.

Method Detail

getInfo

public java.lang.String getInfo()

Returns the name of the model.

Specified by:

getInfo in interface Model

Specified by:

getInfo in class LanguageModel

Returns:

java.lang.String The name of the model.

scoreSeenQuery

public double scoreSeenQuery(double tf,
                             double docLength,
                             double termFrequency,
                             double termEstimate)

The method assigns score for a seen query term.

Specified by:

scoreSeenQuery in class LanguageModel

Parameters:

tf - The within-document frequency.

docLength - The length of the weighted document.

termFrequency - The term frequency in the collection.

termEstimate - The term estimate of the query term.

Returns:

The score for a seen query term.

scoreSeenNonQuery

public double scoreSeenNonQuery(double tf,
                                double docLength,
                                double termFrequency,
                                double termEstimate)

The method assigns score for a seen non-query term.

Specified by:

scoreSeenNonQuery in class LanguageModel

Parameters:

tf - The within-document frequency.

docLength - The length of the weighted document.

termFrequency - The term frequency in the collection.

termEstimate - The term estimate of the query term.

Returns:

The score for a seen non-query term.

scoreUnseenQuery

public double scoreUnseenQuery(double termFrequency)

The method assigns score for a unseen query term.

Specified by:

scoreUnseenQuery in class LanguageModel

Parameters:

termFrequency - The term frequency in the collection.

Returns:

The score for a unseen query term.

scoreUnseenNonQuery

public double scoreUnseenNonQuery(double termFrequency)

The method assigns score for a unseen non-query term.

Specified by:

scoreUnseenNonQuery in class LanguageModel

Parameters:

termFrequency - The term frequency in the collection.

Returns:

The score for a unseen non-query term.

risk

public double risk(double tf,
                   double docLength,
                   double termEstimate)

The method computes the risk of retrieving a seen query term.

Specified by:

risk in class LanguageModel

Parameters:

tf - The within-document frequency.

docLength - The length of the weighted document.

termEstimate - The term estimate of the query term.

Returns:

The risk.

averageTermGenerationProbability

public double averageTermGenerationProbability(int[] tf,
                                               double[] docLength)

The method computes the average term generation probability of a term in vocabulary.

Specified by:

averageTermGenerationProbability in class LanguageModel

Parameters:

tf - An array of within-document frequency of a query term in all documents where it occurs.

docLength - The length of all the documents where the term occurs.

Returns:

The average generation probability.

setNumberOfTokens

public void setNumberOfTokens(double value)

Description copied from interface: Model

Set the number of tokens in the whole collection.

Parameters:

value - The number of tokens in the whole collection.

setAverageDocumentLength

public void setAverageDocumentLength(double a)

Description copied from interface: Model

Set the average document length in the collection.

Parameters:

a - The average document length in the collection.

setNumberOfUniqueTerms

public void setNumberOfUniqueTerms(double n)

Description copied from interface: Model

Set the number of unique terms in the collection.

Parameters:

n - double The number of unique terms in the collection.

setNumberOfPointers

public void setNumberOfPointers(double n)