org.terrier.matching.models
Class TF_IDF

java.lang.Object
  org.terrier.matching.models.WeightingModel
      org.terrier.matching.models.TF_IDF

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Model

public class TF_IDF
extends WeightingModel

This class implements the TF_IDF weighting model. tf is given by Robertson's tf and idf is given by the standard Sparck Jones' idf [Sparck Jones, 1972].

Author:

Ben He, Gianni Amati, Vassilis Plachouras

See Also:

Serialized Form

Field Summary

Fields inherited from class org.terrier.matching.models.WeightingModel

averageDocumentLength, c, documentFrequency, i, keyFrequency, numberOfDocuments, numberOfPointers, numberOfTokens, numberOfUniqueTerms, termFrequency

Constructor Summary

TF_IDF()
A default constructor to make this model.

TF_IDF(double _b)
Constructs an instance of TF_IDF

Method Summary

java.lang.String	getInfo() Returns the name of the model, in this case "TF_IDF"
double	getParameter() Returns the b parameter to the ranking formula as set by setParameter()
double	score(double tf, double docLength) Uses TF_IDF to compute a weight for a term in a document.
double	score(double tf, double docLength, double documentFrequency, double termFrequency, double keyFrequency) Uses TF_IDF to compute a weight for a term in a document.
void	setParameter(double _b) Sets the b parameter to ranking formula

Methods inherited from class org.terrier.matching.models.WeightingModel

clone, getOverflowed, prepare, score, setAverageDocumentLength, setCollectionStatistics, setDocumentFrequency, setEntryStatistics, setKeyFrequency, setNumberOfDocuments, setNumberOfPointers, setNumberOfTokens, setNumberOfUniqueTerms, setRequest, setTermFrequency, stirlingPower

Methods inherited from class java.lang.Object

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

Constructor Detail

TF_IDF

public TF_IDF()

A default constructor to make this model.

TF_IDF

public TF_IDF(double _b)

Constructs an instance of TF_IDF

Parameters:

_b -

Method Detail

getInfo

public final java.lang.String getInfo()

Returns the name of the model, in this case "TF_IDF"

Specified by:

getInfo in interface Model

Specified by:

getInfo in class WeightingModel

Returns:

the name of the model

score

public final double score(double tf,
                          double docLength)

Uses TF_IDF to compute a weight for a term in a document.

Specified by:

score in class WeightingModel

Parameters:

tf - The term frequency of the term in the document

docLength - the document's length

Returns:

the score assigned to a document with the given tf and docLength, and other preset parameters

score

public final double score(double tf,
                          double docLength,
                          double documentFrequency,
                          double termFrequency,
                          double keyFrequency)

Uses TF_IDF to compute a weight for a term in a document.

Specified by:

score in class WeightingModel

Parameters:

tf - The term frequency of the term in the document

docLength - the document's length

documentFrequency - The document frequency of the term (ignored)

termFrequency - the term frequency in the collection (ignored)

keyFrequency - the term frequency in the query (ignored).

Returns:

the score assigned by the weighting model TF_IDF.

setParameter

public void setParameter(double _b)

Sets the b parameter to ranking formula

Specified by:

setParameter in interface Model

Overrides:

setParameter in class WeightingModel

Parameters:

_b - the b parameter value to use.

getParameter

public double getParameter()

Returns the b parameter to the ranking formula as set by setParameter()

Specified by:

getParameter in interface Model

Overrides:

getParameter in class WeightingModel