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sum.js
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sum.js
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(function (_undef) {
"use strict";
/**
* Function wraps the library code to allow passing in the
* dependencies easily.
* @param {Object} _ - Reference to underscore.js
* @param {Object} stemmer - Porter stemmer implementation in js.
* @return {Function} Sumarization function.
*/
var wrapper = function (_, stemmer) {
// Params default values.
var defaults = {
nSentences: 1,
exclude: [],
emphasise: []
};
// regexes
var sentenceDelimiter = /[.!?;]/;
var nGramDelimiter = /[.,!?;]/;
var wordDelimiter = /\s/mg;
var matchJunk = /["#$%&'()*+,\-\/:<=>@\[\\\]\^_`{|}]/mg ;
// List of words which are ignored when computing top relevant sentences.
var stopWords = ["", "a", "about", "above", "above", "across", "after",
"afterwards", "again", "against", "all", "almost", "alone", "along",
"already", "also","although","always","am","among", "amongst",
"amoungst", "amount", "an", "and", "another", "any","anyhow",
"anyone","anything","anyway", "anywhere", "are", "around", "as",
"at", "back","be","became", "because","become","becomes",
"becoming", "been", "before", "beforehand", "behind", "being",
"below", "beside", "besides", "between", "beyond", "bill", "both",
"bottom","but", "by", "call", "can", "cannot", "cant", "co", "con",
"could", "couldnt", "cry", "de", "describe", "detail", "do", "done",
"down", "due", "during", "each", "eg", "eight", "either", "eleven",
"else", "elsewhere", "empty", "enough", "etc", "even", "ever",
"every", "everyone", "everything", "everywhere", "except", "few",
"fifteen", "fify", "fill", "find", "fire", "first", "five", "for",
"former", "formerly", "forty", "found", "four", "from", "front",
"full", "further", "get", "give", "go", "had", "has", "hasnt",
"have", "he", "hence", "her", "here", "hereafter", "hereby",
"herein", "hereupon", "hers", "herself", "him", "himself", "his",
"how", "however", "hundred", "ie", "if", "in", "inc", "indeed",
"interest", "into", "is", "it", "its", "itself", "keep", "last",
"latter", "latterly", "least", "less", "ltd", "made", "many", "may",
"me", "meanwhile", "might", "mill", "mine", "more", "moreover",
"most", "mostly", "move", "much", "must", "my", "myself", "name",
"namely", "neither", "never", "nevertheless", "next", "nine", "no",
"nobody", "none", "noone", "nor", "not", "nothing", "now", "nowhere",
"of", "off", "often", "on", "once", "one", "only", "onto", "or",
"other", "others", "otherwise", "our", "ours", "ourselves", "out",
"over", "own","part", "per", "perhaps", "please", "put", "rather",
"re", "same", "see", "seem", "seemed", "seeming", "seems",
"serious", "several", "she", "should", "show", "side", "since",
"sincere", "six", "sixty", "so", "some", "somehow", "someone",
"something", "sometime", "sometimes", "somewhere", "still", "such",
"system", "take", "ten", "than", "that", "the", "their", "them",
"themselves", "then", "thence", "there", "thereafter", "thereby",
"therefore", "therein", "thereupon", "these", "they", "thickv",
"thin", "third", "this", "those", "though", "three", "through",
"throughout", "thru", "thus", "to", "together", "too", "top",
"toward", "towards", "twelve", "twenty", "two", "un", "under",
"until", "up", "upon", "us", "very", "via", "was", "we", "well",
"were", "what", "whatever", "when", "whence", "whenever", "where",
"whereafter", "whereas", "whereby", "wherein", "whereupon",
"wherever", "whether", "which", "while", "whither", "who",
"whoever", "whole", "whom", "whose", "why", "will", "with",
"within", "without", "would", "yet", "you", "your", "yours",
"yourself", "yourselves", "the"];
/**
* Function used to clean sentences before splitting into words
* @param {String} str
* @return {String}
*/
var clean = function (str) {
return _(str).chain()
.unescapeHTML()
.stripTags()
.clean()
.value()
.replace( matchJunk, '' )
.toLowerCase();
};
/**
* Sentence Module. Creates object with format:
* {orig:String, words:Array<String>, remove:Function}
*/
var Sentence = function (s) {
var c = clean( s );
var all = _.words( c, wordDelimiter );
var words = _(all).chain()
// remove stop words
.filter( function (w) {
return (stopWords.indexOf( w ) === -1) ;
})
// apply stemmer
.map( function (w) {
return stemmer( w );
})
// collect word frequencies
.reduce( function (collect, w) {
collect[w] = collect[w] ? collect[w] + 1 : 1 ;
return collect;
}, {}).value();
// remove a word from this sentence to reduce redundancy in results
var remove = function (w) {
return delete words[w];
};
return {
orig: s,
words: words,
remove: remove
};
};
/**
* Text summarization function.
* @param {Object} opts
* @param {String} opts.corpus - String to summarize.
* @param {String} opts.nWords - Number of words the summary should have.
* @param {String} opts.nSentences - Number of sentences the summary should have.
* @return {Object} output
* @return {Array<String>} output.sentences - The summary sentences in
* order of relevance to the input text.
* @return {String} output.summary - the concatenation of the summary
* sentences for convenience.
*/
var sum = function (opts){
// Handle options.
opts = _.extend( {}, defaults, opts );
opts.corpus = opts.corpus || _undef;
if (opts.corpus === _undef) {
throw Error( 'No input corpus' );
}
if (opts.nWords !== _undef && !_.isNumber(opts.nWords)) {
throw Error('Bad value for nWords');
}
// Clean corpus.
var s = opts.corpus.split(sentenceDelimiter);
var sentences = _(s).map( function (s) {
return new Sentence(s);
});
// Splits the sentences into nGrams then applies the same algorithm.
if (opts.nWords) {
// `opts.nSentences` is ignored, output size is determined by lexem size.
opts.nSentences = 1;
var nGrams = _(sentences).reduce( function (collect, s) {
var orig = s.orig;
var partials = _(s.words).reduce( function (memo, freq, w) {
var pos = orig.indexOf(' ');
if (pos === -1) {
pos = orig.length;
}
var partial = orig.substr(0, pos);
orig = orig.substr(pos + 1);
if (partial !== '') {
memo.push(partial);
}
return memo;
}, []);
if (partials.length <= opts.nWords) {
var newSentence = new Sentence( partials.join(' '));
collect.push( newSentence );
return collect;
}
var i = 0,
j = 0,
n = partials.length - opts.nWords,
m = partials.length,
tmp;
for (i = 0; i < n; i ++) {
var tmp = ''
for (j = i; j < i+opts.nWords; j ++) {
tmp += partials[j] + ' ';
}
var newSentence = new Sentence(tmp);
collect.push(newSentence);
}
return collect;
}, []);
sentences = nGrams;
}
/**
* Return all sentences that contain a givven word.
* @param {String} w - word
* @return {Array<Object>}
*/
var containing = function (w) {
return _(sentences).filter( function (s) {
return (s.words[w] !== undefined) ;
});
};
// If summary must exclude words in opts.exclude remove sentences
// that contain those words.
if ( _.isArray(opts.exclude) && opts.exclude.length !== 0) {
var excludes = _(opts.exclude).map( function (w) {
return stemmer(clean(w));
});
sentences = _(sentences).filter( function (s) {
var words = _(s.words).keys();
return (_.intersection( words, excludes ).length === 0);
});
}
var summary = [];
var counter = 0;
// Extract sentences in order of their relevance.
while (true) {
var N = sentences.length;
// Builds a hash of all words with global frequencies.
var words = _(sentences).reduce( function (collect,s) {
_(s.words).each( function (count, w) {
collect[w] = collect[w] ? collect[w] + count : count ;
});
return collect;
}, {});
// If summary must have the words in opts.emphasise.
var emphasise = [];
if ( _.isArray(opts.emphasise) && opts.emphasise.length !== 0) {
emphasise = _(opts.emphasise).map( function (w) {
return stemmer(clean(w));
});
}
// Calculate relevance for each sentence.
_(sentences).each( function (s) {
var relevance = _(s.words).reduce( function (memo, freq, w) {
var local = Math.log(1 + freq);
var global = Math.log(N / containing(w).length);
return memo = memo + (local * global);
}, 0);
// If current sentence containes emphasised words,
// bumb up the relevance.
var bump = _.intersection(emphasise, _(s.words).keys()).length;
relevance += bump * 1000;
s.relevance = relevance;
})
// Highest relevance sentence.
var highest = _(sentences).max( function (s) {
return s.relevance;
});
// Remove words from the remaining sentences to reduce redundancy.
sentences = _(sentences).chain()
.without(highest)
.map( function (s) {
_(highest.words).each( function (w) {
s.remove( w );
});
return s;
})
.value();
summary.push( highest.orig ) ;
counter += 1;
var stop = (counter === opts.nSentences || sentences.length === 0);
if (stop) break;
}
return {
'summary': summary.join('.'),
'sentences': summary
};
};
return sum;
};
// exports the `sum` function in node.js
if (typeof exports !== 'undefined'
&& typeof module !== 'undefined'
&& module.exports
&& typeof require !== 'undefined') {
var stemmer = require( 'porter-stemmer' ).stemmer;
var _ = require( 'underscore' );
_.str = require( 'underscore.string' );
_.mixin( _.str.exports() );
module.exports = wrapper(_, stemmer);
}
// exports `sum` to AMD module, defining dependencies
else if (typeof define === 'function' && define.amd) {
define('sum', [
'underscore',
'underscore.string',
'porter-stemmer'
], function(_, str, stemmer) {
return wrapper(_, stemmer);
});
}
// export in browser
else if (typeof this !== 'undefined'
&& this._ && this.stemmer) {
this._.mixin( this._.str.exports() );
this.sum = wrapper(this._, this.stemmer);
}
else {
throw Error( 'Unsupported js environment detected' );
}
}).call(this);