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 Details

### 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 Details

### 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`
Parameters:
  `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)`