Package org.apache.lucene.search.similarities

Class NormalizationZ

java.lang.Object

org.apache.lucene.search.similarities.Normalization

org.apache.lucene.search.similarities.NormalizationZ

public class NormalizationZ
extends Normalization

Pareto-Zipf Normalization

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	Description
NormalizationZ()	Calls NormalizationZ(0.3)
NormalizationZ(float z)	Creates NormalizationZ with the supplied parameter z.

Method Summary

Modifier and Type	Method	Description
Explanation	explain(BasicStats stats, double tf, double len)	Returns an explanation for the normalized term frequency.
float	getZ()	Returns the parameter z
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

NormalizationZ

public NormalizationZ()

Calls NormalizationZ(0.3)

NormalizationZ

public NormalizationZ(float z)

Creates NormalizationZ with the supplied parameter z.

Parameters:

z - represents A/(A+1) where A measures the specificity of the language. It ranges from (0 .. 0.5)

Method Detail

tfn

public 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

getZ

public float getZ()

Returns the parameter z

See Also:

NormalizationZ(float)