org.apache.lucene.classification

Class KNearestNeighborClassifier

java.lang.Object

org.apache.lucene.classification.KNearestNeighborClassifier

All Implemented Interfaces:

Classifier<BytesRef>

Direct Known Subclasses:

KNearestNeighborDocumentClassifier

public class KNearestNeighborClassifier
extends Object
implements Classifier<BytesRef>

A k-Nearest Neighbor classifier (see http://en.wikipedia.org/wiki/K-nearest_neighbors) based on MoreLikeThis

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field and Description
protected String	classFieldName the name of the field used as the output text
protected IndexSearcher	indexSearcher an IndexSearcher used to perform queries
protected int	k the no.
protected MoreLikeThis	mlt a MoreLikeThis instance used to perform MLT queries
protected Query	query a Query used to filter the documents that should be used from this classifier's underlying LeafReader
protected String[]	textFieldNames the name of the fields used as the input text

Constructor Summary

Constructors

Constructor and Description
KNearestNeighborClassifier(IndexReader indexReader, Similarity similarity, Analyzer analyzer, Query query, int k, int minDocsFreq, int minTermFreq, String classFieldName, String... textFieldNames) Creates a KNearestNeighborClassifier.

Method Summary

Modifier and Type	Method and Description
ClassificationResult<BytesRef>	assignClass(String text) Assign a class (with score) to the given text String
protected List<ClassificationResult<BytesRef>>	buildListFromTopDocs(TopDocs topDocs) build a list of classification results from search results
protected ClassificationResult<BytesRef>	classifyFromTopDocs(TopDocs knnResults) TODO
List<ClassificationResult<BytesRef>>	getClasses(String text) Get all the classes (sorted by score, descending) assigned to the given text String.
List<ClassificationResult<BytesRef>>	getClasses(String text, int max) Get the first max classes (sorted by score, descending) assigned to the given text String.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

mlt

protected final MoreLikeThis mlt

a MoreLikeThis instance used to perform MLT queries

textFieldNames

protected final String[] textFieldNames

the name of the fields used as the input text

classFieldName

protected final String classFieldName

the name of the field used as the output text

indexSearcher

protected final IndexSearcher indexSearcher

an IndexSearcher used to perform queries

k

protected final int k

the no. of docs to compare in order to find the nearest neighbor to the input text

query

protected final Query query

a Query used to filter the documents that should be used from this classifier's underlying LeafReader

Constructor Detail

KNearestNeighborClassifier

public KNearestNeighborClassifier(IndexReader indexReader,
                                  Similarity similarity,
                                  Analyzer analyzer,
                                  Query query,
                                  int k,
                                  int minDocsFreq,
                                  int minTermFreq,
                                  String classFieldName,
                                  String... textFieldNames)

Creates a KNearestNeighborClassifier.

Parameters:

indexReader - the reader on the index to be used for classification

analyzer - an Analyzer used to analyze unseen text

similarity - the Similarity to be used by the underlying IndexSearcher or null (defaults to BM25Similarity)

query - a Query to eventually filter the docs used for training the classifier, or null if all the indexed docs should be used

k - the no. of docs to select in the MLT results to find the nearest neighbor

minDocsFreq - MoreLikeThis.minDocFreq parameter

minTermFreq - MoreLikeThis.minTermFreq parameter

classFieldName - the name of the field used as the output for the classifier

textFieldNames - the name of the fields used as the inputs for the classifier, they can contain boosting indication e.g. title^10

Method Detail

assignClass

public ClassificationResult<BytesRef> assignClass(String text)
                                           throws IOException

Assign a class (with score) to the given text String

Specified by:

assignClass in interface Classifier<BytesRef>

Parameters:

text - a String containing text to be classified

Returns:

a ClassificationResult holding assigned class of type T and score

Throws:

IOException - If there is a low-level I/O error.

classifyFromTopDocs

protected ClassificationResult<BytesRef> classifyFromTopDocs(TopDocs knnResults)
                                                      throws IOException

TODO

Throws:

IOException

getClasses

public List<ClassificationResult<BytesRef>> getClasses(String text)
                                                throws IOException

Get all the classes (sorted by score, descending) assigned to the given text String.

Specified by:

getClasses in interface Classifier<BytesRef>

Parameters:

text - a String containing text to be classified

Returns:

the whole list of ClassificationResult, the classes and scores. Returns null if the classifier can't make lists.

Throws:

IOException - If there is a low-level I/O error.

getClasses

public List<ClassificationResult<BytesRef>> getClasses(String text,
                                                       int max)
                                                throws IOException

Get the first max classes (sorted by score, descending) assigned to the given text String.

Specified by:

getClasses in interface Classifier<BytesRef>

Parameters:

text - a String containing text to be classified

max - the number of return list elements

Returns:

the whole list of ClassificationResult, the classes and scores. Cut for "max" number of elements. Returns null if the classifier can't make lists.

Throws:

IOException - If there is a low-level I/O error.

buildListFromTopDocs

protected List<ClassificationResult<BytesRef>> buildListFromTopDocs(TopDocs topDocs)
                                                             throws IOException

build a list of classification results from search results

Parameters:

topDocs - the search results as a TopDocs object

Returns:

a List of ClassificationResult, one for each existing class

Throws:

IOException - if it's not possible to get the stored value of class field

toString

public String toString()

Overrides:

toString in class Object