In_expB2 (Terrier Information Retrieval Platform 5.5 API)

java.lang.Object
- org.terrier.matching.models.WeightingModel
- - org.terrier.matching.models.In_expB2

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Model
```
public class In_expB2
extends WeightingModel
```
This class implements the In_expB2 weighting model, namely Inverse Expected Document Frequency model with Bernoulli after-effect and normalisation 2. The logarithms are base 2. This model can be used for classic ad-hoc tasks.

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

In_expB2()
A default constructor.

In_expB2(double c)
Constructs an instance of this class with the specified value for the parameter beta.

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)`	This method provides the contract for implementing weighting models.

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
  - In_expB2
```
public In_expB2()
```
    A default constructor. This must be followed by specifying the c value.
  - In_expB2
```
public In_expB2(double c)
```
    Constructs an instance of this class with the specified value for the parameter beta.
    
    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)
```
    This method provides the contract for implementing weighting models.
    
    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