org.terrier.matching.models
Class LGD

java.lang.Object
  extended by org.terrier.matching.models.WeightingModel
      extended by org.terrier.matching.models.LGD
All Implemented Interfaces:
java.io.Serializable, java.lang.Cloneable, Model

public class LGD
extends WeightingModel

This class implements the LGD weighting model. For more information about this model, see:

  1. Stephane Clinchant and Eric Gaussier. Bridging Language Modeling and Divergence From Randomness Approaches: A Log-logistic Model for IR. ICTIR 2009, London, UK.
  2. Stephane Clinchant and Eric Gaussier. Information-Based Models for Ad Hoc Information Retrieval. SIGIR 2010, Geneva, Switzerland.

Author:
Gianni Amati
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
LGD()
          A default constructor.
LGD(double c)
          Constructs an instance of this class with the specified value for the parameter c.
 
Method Summary
 java.lang.String getInfo()
          Returns the name of the model.
 double score(double tf, double docLength)
          Uses LGD to compute a weight for a term in a document.
 double score(double tf, double docLength, double n_t, double F_t, double keyFrequency)
          Uses LGD to compute a weight for a term in a document.
 
Methods inherited from class org.terrier.matching.models.WeightingModel
clone, getOverflowed, getParameter, prepare, score, setAverageDocumentLength, setCollectionStatistics, setDocumentFrequency, setEntryStatistics, setKeyFrequency, setNumberOfDocuments, setNumberOfPointers, setNumberOfTokens, setNumberOfUniqueTerms, setParameter, setRequest, setTermFrequency, stirlingPower
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

LGD

public LGD()
A default constructor. This must be followed by specifying the c value.


LGD

public LGD(double c)
Constructs an instance of this class with the specified value for the parameter c.

Parameters:
c - the term frequency normalisation parameter value.
Method Detail

getInfo

public final java.lang.String getInfo()
Returns the name of the model.

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 LGD to compute a weight for a term in a document.

Specified by:
score in class WeightingModel
Parameters:
tf - The term frequency 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 n_t,
                          double F_t,
                          double keyFrequency)
Uses LGD to compute a weight for a term in a document.

Specified by:
score in class WeightingModel
Parameters:
tf - The term frequency in the document
docLength - the document's length
n_t - The document frequency of the term
F_t - the term frequency in the collection
keyFrequency - the term frequency in the query
Returns:
the score assigned by the weighting model LGD.


Terrier 3.5. Copyright © 2004-2011 University of Glasgow