org.apache.lucene.search.similarities

Class NormalizationH2

java.lang.Object

org.apache.lucene.search.similarities.Normalization

org.apache.lucene.search.similarities.NormalizationH2

public class NormalizationH2
extends Normalization

Normalization model in which the term frequency is inversely related to the length.

While this model is parameterless in the original article, the thesis introduces the parameterized variant. The default value for the c parameter is 1.

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.Normalization

Normalization.NoNormalization

Constructor Summary

Constructors

Constructor and Description
NormalizationH2() Calls NormalizationH2(1)
NormalizationH2(float c) Creates NormalizationH2 with the supplied parameter c.

Method Summary

Modifier and Type	Method and Description
Explanation	explain(BasicStats stats, double tf, double len) Returns an explanation for the normalized term frequency.
float	getC() Returns the c parameter.
double	tfn(BasicStats stats, double tf, double len) Returns the normalized term frequency.
String	toString() Subclasses must override this method to return the code of the normalization formula.

Methods inherited from class java.lang.Object

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

Constructor Detail

NormalizationH2

public NormalizationH2(float c)

Creates NormalizationH2 with the supplied parameter c.

Parameters:

c - hyper-parameter that controls the term frequency normalization with respect to the document length.

NormalizationH2

public NormalizationH2()

Calls NormalizationH2(1)

Method Detail

tfn

public final double tfn(BasicStats stats,
                        double tf,
                        double len)

Description copied from class: Normalization

Returns the normalized term frequency.

Specified by:

tfn in class Normalization

len - the field length.

explain

public Explanation explain(BasicStats stats,
                           double tf,
                           double len)

Description copied from class: Normalization

Returns an explanation for the normalized term frequency.

The default normalization methods use the field length of the document and the average field length to compute the normalized term frequency. This method provides a generic explanation for such methods. Subclasses that use other statistics must override this method.

Overrides:

explain in class Normalization

toString

public String toString()

Description copied from class: Normalization

Subclasses must override this method to return the code of the normalization formula. Refer to the original paper for the list.

Specified by:

toString in class Normalization

getC

public float getC()

Returns the c parameter.

See Also:

NormalizationH2(float)