DPH (Terrier Information Retrieval Platform 5.5 API)

java.lang.Object
- org.terrier.matching.models.WeightingModel
- - org.terrier.matching.models.DPH

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Model
```
public class DPH
extends WeightingModel
```
This class implements the DPH hypergeometric weighting model. P stands for Popper's normalization. This is a parameter-free weighting model. Even if the user specifies a parameter value, it will NOT affect the results. It is highly recomended to use the model with query expansion.
References
1. FUB, IASI-CNR and University of Tor Vergata at TREC 2007 Blog Track. G. Amati and E. Ambrosi and M. Bianchi and C. Gaibisso and G. Gambosi. Proceedings of the 16th Text REtrieval Conference (TREC-2007), 2008.
2. Frequentist and Bayesian approach to Information Retrieval. G. Amati. In Proceedings of the 28th European Conference on IR Research (ECIR 2006). LNCS vol 3936, pages 13--24.
Author:

Gianni Amati, Ben He, Vassilis Plachouras

See Also:

Serialized Form

Field Summary
- Fields inherited from class org.terrier.matching.models.WeightingModel
  averageDocumentLength, c, cs, documentFrequency, es, i, keyFrequency, numberOfDocuments, numberOfPointers, numberOfPostings, numberOfTokens, numberOfUniqueTerms, rq, termFrequency

Constructor Summary

Constructors
Constructor Description

DPH()
A default constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`java.lang.String`	`getInfo()`	Returns the name of the model.
`double`	`score(double tf, double docLength)`	Uses DPH to compute a weight for a term in a document.

Methods inherited from class org.terrier.matching.models.WeightingModel
clone, getOverflowed, getParameter, prepare, score, setCollectionStatistics, setEntryStatistics, setKeyFrequency, setParameter, setRequest

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DPH
```
public DPH()
```
    A default constructor.
- 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 DPH 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