Jeff Kubina > Text-Categorize-Textrank > Text::Categorize::Textrank::En

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Module Version: 0.51   Source  

NAME ^

Text::Categorize::Textrank::En - Find potential keywords in English text.

SYNOPSIS ^

  use strict;
  use warnings;
  use Text::Categorize::Textrank::En;
  use Data::Dump qw(dump);
  my $textrankerEn = Text::Categorize::Textrank::En->new();
  my $text         = 'This is the first sentence. Here is the second sentence.';
  my $results      = $textrankerEn->getTextrankInfoOfText(listOfText => [$text]);
  dump $results->{hashOfTextrankValues};

DESCRIPTION ^

Text::Categorize::Textrank::En provides methods for ranking the words in English text as potential keywords. It implements a version of the textrank algorithm from the report TextRank: Bringing Order into Texts by R. Mihalcea and P. Tarau.

Encoding of all text should be in Perl's internal format; see Text::Iconv or Encode for converting text from various encodings.

CONSTRUCTOR ^

new

The method new creates an instance of the Text::Categorize::Textrank::En class with the following parameters:

endingSentenceTag
 endingSentenceTag => 'PP'

endingSentenceTag is the part-of-speech tag that should be used to indicate the end of a sentence. The default is 'PP'. The value of this tag must be a tag generated by the module Lingua::EN::Tagger.

listOfPOSTypesToKeep
 listOfPOSTypesToKeep => [qw(TEXTRANK_WORDS)]

The textrank algorithm preprocesses the text so that only certain parts-of-speech (POS) are retained and used to build the graph representing the text. The module Lingua::EN::Tagger is used to tag the parts-of-speech of the text. The parts-of-speech retained can be specified by word types, where the type is a combination of 'ALL', 'ADJECTIVES', 'ADVERBS', 'CONTENT_WORDS', 'NOUNS', 'PUNCTUATION', 'TEXTRANK_WORDS', or 'VERBS'. The default is [qw(TEXTRANK_WORDS)], which equates to [qw(ADJECTIVES NOUNS)].

listOfPOSTagsToKeep
 listOfPOSTagsToKeep => [...]

listOfPOSTagsToKeep provides finer control over the parts-of-speech to be retained when filtering the tagged text. For a list of all the possible tags call getListOfPartOfSpeechTags().

METHODS ^

getTextrankInfoOfText

 getTextrankInfoOfText (...)

The method getTextrankInfoOfText returns a data structure (hash-reference) containing all the stemmed words partitioned into their sentences (listOfStemmedTaggedSentences), the subset of words used to compute the textranks (listOfFilteredSentences), and the textrank of the tokens (hashOfTextrankValues) that occur in listOfFilteredSentences. The sum of all the textrank values is one.

More precisely, if $results is the returned hash, then $results->{listOfStemmedTaggedSentences} contains the array reference generated by the getStemmedAndTaggedText method of Text::StemTagPOS, $results->{listOfFilteredSentences} contains the array reference generated by getTaggedTextToKeep of Text::StemTagPOS, and $results->{hashOfTextrankValues} holds the hash of the textrank values computed by getTextrankOfListOfTokens. $results->{useStemmedWords} is also set to the value of useStemmedWords.

listOfStemmedTaggedSentences
 listOfStemmedTaggedSentences => [...]

listOfStemmedTaggedSentences is the array reference containing the list of stemmed and part-of-speech tagged sentences from Text::StemTagPos. If listOfStemmedTaggedSentences is not defined, then the text to be processed should be provided via listOfText.

listOfText
 listOfText => [...]

listOfText is an array reference containing the strings of text to be categorized. listOfText is only used if listOfStemmedTaggedSentences is undefined.

edgeCreationSpan
  edgeCreationSpan => 1

For each word in the text, edgeCreationSpan is the number of successive words used to make an edge in the textrank token graph. For example, if tokenEdgeSpanSize is two, then given the word sequence "apple orange pear" the edges [apple, orange] and [apple, pear] will be added to the text graph for the word apple. The default is one.

Note that loop edges are ignored. For example, if edgeCreationSpan is two, then given the word sequence "daba daba doo" the edge [daba, daba] is disguarded but the edge [daba, doo] is added to the token graph.

directedGraph
  directedGraph => 0

If directedGraph is true, the textranks are computed from the directed token graph, if false, they are computed from the undirected version of the graph. The default is false.

pageRankDampeningFactor
  pageRankDampeningFactor => 0.85

When computing the textranks of the token graph, the dampening factor specified by pageRankDampeningFactor will be used; it should range from zero to one. The default is 0.85.

The Wikipedia article on pagerank has a good explaination of the dampening factor.
 
addEdgesSpanningSentences
  addEdgesSpanningLists => 1

If addEdgesSpanningLists is true, then when building the token graph, links between the tokens at the end of a list and the beginning of the next list will be made. For example, for the lists [[qw(This is the first list)], [qw(Here is the second list)]] the edge [list, Here] will be added to the token graph. The default is true.

useStemmedWords
  useStemmedWords => 1

If useStemmedWords is true, then when building the token graph, the stemmed words are used as the id of each node, otherwise the original words are used; in both cases the stemmed or original words are converted to lowercase. The default is true.

INSTALLATION ^

To install the module run the following commands:

  perl Makefile.PL
  make
  make test
  make install

If you are on a windows box you should use 'nmake' rather than 'make'.

BUGS ^

Please email bugs reports or feature requests to bug-text-categorize-textrank-en@rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Text-Categorize-Textrank-En. The author will be notified and you can be automatically notified of progress on the bug fix or feature request.

AUTHOR ^

 Jeff Kubina<jeff.kubina@gmail.com>

COPYRIGHT ^

Copyright (c) 2009 Jeff Kubina. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

KEYWORDS ^

categorize, english, keywords, keyprhases, nlp, pagerank, textrank

SEE ALSO ^

This package implements the Textrank algorithm from the report TextRank: Bringing Order into Texts by Rada Mihalcea and Paul Tarau; which is related to pagerank. See the Lingua::EN::Tagger README file for a list of the part-of-speech tags.

Lingua::EN::Tagger, Lingua::Stem::Snowball, Log::Log4perl, Text::Categorize::Textrank, Text::StemTagPOS

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