org.apache.lucene.search.similarities

Class AxiomaticF3LOG

java.lang.Object

org.apache.lucene.search.similarities.Similarity

org.apache.lucene.search.similarities.SimilarityBase

org.apache.lucene.search.similarities.Axiomatic

org.apache.lucene.search.similarities.AxiomaticF3LOG

public class AxiomaticF3LOG
extends Axiomatic

F2EXP is defined as Sum(tf(term_doc_freq)*IDF(term)-gamma(docLen, queryLen)) where IDF(t) = ln((N+1)/df(t)) N=total num of docs, df=doc freq gamma(docLen, queryLen) = (docLen-queryLen)*queryLen*s/avdl

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.search.similarities.Similarity

Similarity.SimScorer, Similarity.SimWeight

Field Summary

Fields inherited from class org.apache.lucene.search.similarities.Axiomatic

k, queryLen, s

Fields inherited from class org.apache.lucene.search.similarities.SimilarityBase

discountOverlaps

Constructor Summary

Constructors

Constructor and Description
AxiomaticF3LOG(float s, int queryLen) Constructor setting s and queryLen, letting k to default

Method Summary

Modifier and Type	Method and Description
protected float	gamma(BasicStats stats, float freq, float docLen) compute the gamma component
protected float	idf(BasicStats stats, float freq, float docLen) compute the inverted document frequency component
protected float	ln(BasicStats stats, float freq, float docLen) compute the document length component
protected float	tf(BasicStats stats, float freq, float docLen) compute the term frequency component
protected float	tfln(BasicStats stats, float freq, float docLen) compute the mixed term frequency and document length component
String	toString() Name of the axiomatic method.

Methods inherited from class org.apache.lucene.search.similarities.Axiomatic

explain, score

Methods inherited from class org.apache.lucene.search.similarities.SimilarityBase

computeNorm, computeWeight, explain, fillBasicStats, getDiscountOverlaps, log2, newStats, setDiscountOverlaps, simScorer

Methods inherited from class java.lang.Object

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

Constructor Detail

AxiomaticF3LOG

public AxiomaticF3LOG(float s,
                      int queryLen)

Constructor setting s and queryLen, letting k to default

Parameters:

s - hyperparam for the growth function

queryLen - the query length

Method Detail

toString

public String toString()

Description copied from class: Axiomatic

Name of the axiomatic method.

Specified by:

toString in class Axiomatic

tf

protected float tf(BasicStats stats,
                   float freq,
                   float docLen)

compute the term frequency component

Specified by:

tf in class Axiomatic

ln

protected float ln(BasicStats stats,
                   float freq,
                   float docLen)

compute the document length component

Specified by:

ln in class Axiomatic

tfln

protected float tfln(BasicStats stats,
                     float freq,
                     float docLen)

compute the mixed term frequency and document length component

Specified by:

tfln in class Axiomatic

idf

protected float idf(BasicStats stats,
                    float freq,
                    float docLen)

compute the inverted document frequency component

Specified by:

idf in class Axiomatic

gamma

protected float gamma(BasicStats stats,
                      float freq,
                      float docLen)

compute the gamma component

Specified by:

gamma in class Axiomatic