Class LMSimilarity

Abstract superclass for language modeling Similarities. The following inner types are introduced:

  • LMSimilarity.LMStats, which defines a new statistic, the probability that the collection language model generates the current term;
  • LMSimilarity.ICollectionModel, which is a strategy interface for object that compute the collection language model p(w|C);
  • LMSimilarity.DefaultCollectionModel, an implementation of the former, that computes the term probability as the number of occurrences of the term in the collection, divided by the total number of tokens.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk
Inheritance
System.Object
Similarity
SimilarityBase
LMSimilarity
LMDirichletSimilarity
LMJelinekMercerSimilarity
Inherited Members
Namespace: Lucene.Net.Search.Similarities
Assembly: Lucene.Net.dll
Syntax
public abstract class LMSimilarity : SimilarityBase

Constructors

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LMSimilarity()

Creates a new instance with the default collection language model.

Declaration
public LMSimilarity()
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LMSimilarity(LMSimilarity.ICollectionModel)

Creates a new instance with the specified collection language model.

Declaration
public LMSimilarity(LMSimilarity.ICollectionModel collectionModel)
Parameters
Type Name Description
LMSimilarity.ICollectionModel collectionModel

Fields

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m_collectionModel

The collection model.

Declaration
protected readonly LMSimilarity.ICollectionModel m_collectionModel
Field Value
Type Description
LMSimilarity.ICollectionModel

Methods

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Explain(Explanation, BasicStats, Int32, Single, Single)

Declaration
protected override void Explain(Explanation expl, BasicStats stats, int doc, float freq, float docLen)
Parameters
Type Name Description
Explanation expl
BasicStats stats
System.Int32 doc
System.Single freq
System.Single docLen
Overrides
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FillBasicStats(BasicStats, CollectionStatistics, TermStatistics)

Computes the collection probability of the current term in addition to the usual statistics.

Declaration
protected override void FillBasicStats(BasicStats stats, CollectionStatistics collectionStats, TermStatistics termStats)
Parameters
Type Name Description
BasicStats stats
CollectionStatistics collectionStats
TermStatistics termStats
Overrides
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GetName()

Returns the name of the LM method. The values of the parameters should be included as well.

Used in ToString()

.

Declaration
public abstract string GetName()
Returns
Type Description
System.String
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NewStats(String, Single)

Declaration
protected override BasicStats NewStats(string field, float queryBoost)
Parameters
Type Name Description
System.String field
System.Single queryBoost
Returns
Type Description
BasicStats
Overrides
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ToString()

Returns the name of the LM method. If a custom collection model strategy is used, its name is included as well.

Declaration
public override string ToString()
Returns
Type Description
System.String
Overrides
See Also