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sum.js
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sum.js
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// TODO register cleanup function ;)
var sum = (function(win,undef){
"use strict" ;
var newWord = function( word ) {
if( typeof word !== 'string' ){
return undef ;
}
return {
'word' : word ,
'gwf' : 1
} ;
} ;
var newSentence = function( sentence, cleanSentence ) {
if( typeof sentence !== 'string' && typeof cleanSentence !== 'string' ){
return undef ;
}
return {
sentence : sentence ,
cleanSentence : cleanSentence ,
wordHash : {} ,
lwf : {}
} ;
} ;
var matchJunk = /["#$%&'()*+,\-\/:<=>@\[\\\]\^_`{|}]/mg ;
var matchMultipleSpaces = /\s{2,}/mg ;
var sentenceSplitter = /[.!?;]/ ;
var wordSplitter = /\s/mg ;
var localWeight = function( wordObj, sentenceObj ) {
//return Math.log( 1 + sentenceObj.lwf[ wordObj.word ] ) ;
var maxFreq = 0 ;
for( var w in sentenceObj.wordHash ) {
if( maxFreq < sentenceObj.lwf[w] ){
maxFreq = sentenceObj.lwf[w] ;
}
}
return (1+sentenceObj.lwf[w]/maxFreq)/2 ;
} ;
var sum = function( corpus , params ) { // params.size - nr of sentences in output
// defaults
params = params || {} ;
params.size = params.size || 1 ;
var wordHash = {} ; // global word hash
var sentenceHash = {} ;
// clean version of the corpus
var cleanCorpus = corpus
.replace( matchJunk , '' ) // leaves out .!?; and all spaces
.replace( matchMultipleSpaces , ' ' ) ; // removes multiple spaces and keeps just one
var sentences = corpus.split( sentenceSplitter ).filter( function(sentence){
return ( sentence !== ' ' && sentence !== '' ) ; //TODO externalize
}) ;
var N = sentences.length ;
var cleanSentences = cleanCorpus.split( sentenceSplitter ).filter( function(sentence){
return ( sentence !== ' ' && sentence !== '' ) ; //TODO externalize
});
//TODO check if cleanSentences.length === N. if not throw an error
for( var i = 0, len = sentences.length ; i < len ; i ++ ) {
var s = sentences[ i ] ;
var cs = cleanSentences[ i ] ;
var sent = sentenceHash[ s ] = newSentence( s, cs ) ;
var cleanWords = cs.split( wordSplitter ).filter( function(word){ //TODO externalize word filter func
return ( word !== ' ' && word !== '' ) ;
}) ;
for( var j = 0, lenW = cleanWords.length ; j < lenW ; j ++ ) {
var w = cleanWords[j] ;
if( wordHash[ w ] === undef ) {
wordHash[ w ] = newWord( w ) ;
}
else {
wordHash[ w ].gwf ++ ; // increase global word frequency
}
if( sent.wordHash[ w ] === undef ) {
sent.wordHash[ w ] = wordHash[ w ] ;
sent.lwf[ w ] = 1 ;
}
else {
sent.lwf[ w ] ++ ;
}
}
}
var removeSentence = function( sentenceObj ) { // param: the sentence object
for( w in sentenceObj.wordHash ) {
if( sentenceObj.wordHash.hasOwnProperty( w ) ){
wordHash[w] = undef ; // removes from all sentences and global word hash
}
}
sentenceHash[ sentenceObj.cleanSentence ] = undef ;
N = N - 1 ;
} ;
var globalWeight = function( wordObj ){
var ni = 0 ;
for( var i in sentenceHash ) {
if( sentenceHash.hasOwnProperty( i ) ){
var s = sentenceHash[i] ;
if( s.wordHash[ wordObj.word ] !== undef ){
ni ++ ;
}
}
}
return Math.log( N / ni ) ;
} ;
var relevanceScore = function( sentenceObj ) { //TODO momoization wouldn't hurt
var score = 0, w, lw, gw ;
for( var i in sentenceObj.wordHash ) {
if( sentenceObj.wordHash.hasOwnProperty( i ) ) {
w = sentenceObj.wordHash[i] ;
lw = localWeight( w , sentenceObj ) ;
gw = globalWeight( w ) ;
score += lw * gw ;
}
}
return score ;
} ;
var summary = '' ;
for( var k = 1 ; k <= params.size ; k ++ ) {
// 1. sort descending sententece by relevance score
sentences.sort( function( s1, s2 ){
var rs1 = relevanceScore( sentenceHash[ s1 ] ) ;
var rs2 = relevanceScore( sentenceHash[ s2 ] ) ;
if( rs1 < rs2 ) {
return 1 ;
}
else {
if( rs1 > rs2 ) {
return -1 ;
}
else {
return 0 ;
}
}
}) ;
// 2. remove sentence
var topScoringSentence = sentences.splice(0,1) ;
removeSentence( topScoringSentence ) ;
// 3. add to summary
summary += topScoringSentence ;
}
return summary ;
} ; //~ end sum()
return sum ;
})() ;