Class LMJelinekMercerSimilarity

Language model based on the Jelinek-Mercer smoothing method. From Chengxiang Zhai and John Lafferty. 2001. A study of smoothing methods for language models applied to Ad Hoc information retrieval. In Proceedings of the 24th annual international ACM SIGIR conference on Research and development in information retrieval (SIGIR '01). ACM, New York, NY, USA, 334-342.

The model has a single parameter, λ. According to said paper, the optimal value depends on both the collection and the query. The optimal value is around 0.1 for title queries and 0.7 for long queries.

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

Constructors

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LMJelinekMercerSimilarity(LMSimilarity.ICollectionModel, Single)

Instantiates with the specified collectionModel and λ parameter.

Declaration
public LMJelinekMercerSimilarity(LMSimilarity.ICollectionModel collectionModel, float lambda)
Parameters
Type Name Description
LMSimilarity.ICollectionModel collectionModel
System.Single lambda
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LMJelinekMercerSimilarity(Single)

Instantiates with the specified λ parameter.

Declaration
public LMJelinekMercerSimilarity(float lambda)
Parameters
Type Name Description
System.Single lambda

Properties

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Lambda

Returns the λ parameter.

Declaration
public virtual float Lambda { get; }
Property Value
Type Description
System.Single

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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GetName()

Declaration
public override string GetName()
Returns
Type Description
System.String
Overrides
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Score(BasicStats, Single, Single)

Declaration
public override float Score(BasicStats stats, float freq, float docLen)
Parameters
Type Name Description
BasicStats stats
System.Single freq
System.Single docLen
Returns
Type Description
System.Single
Overrides