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train.js
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train.js
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// keep track of documents per language
var documents = {
french : 0,
spanish : 0,
english : 0,
german : 0,
basque : 0
};
// words instances across all languages
// e.g. {banana: 13, and: 5, blanco: 2, en: 6}
var wordsTotal = {};
// word instances per language
// e.g. banana : {english: 5, french: 4, spanish: 4}
var wordsPerLanguage = {};
// process training documents
var train = function (document, language) {
// increment document count
documents[language] += 1;
// extract word array from document
var words = tokenize(document);
var length = words.length;
// increment words total and words per language
for (var i = 0; i < length; i++)
incrementWords(words[i], language);
};
// filtering function, removes duplicates
function unique(value, index, self) {
return self.indexOf(value) === index;
}
// create tokens from document
var tokenize = function (text) {
text = text.toLowerCase();
// remove non-alphanumeric chars
text = text.replace(/\W/g, ' ');
// replace blank segments with single blank space
text = text.replace(/\s+/g, ' ');
// remove leading/trailing whitespace
text = text.trim();
// create array using empty space as separator
text = text.split(' ');
// remove duplicate words
text = text.filter(unique);
return text;
};
// add to words total and words per language
var incrementWords = function (word, language) {
// add to wordsTotal
if (word in wordsTotal){
wordsTotal[word] += 1;
}
else{
wordsTotal[word] = 1;
}
// add wordsPerLanguage
if (word in wordsPerLanguage){
if (language in wordsPerLanguage[word]){
wordsPerLanguage[word][language] += 1;
}
else{
wordsPerLanguage[word][language] = 1;
}
}
else{
wordsPerLanguage[word] = {};
wordsPerLanguage[word][language] = 1;
}
};
function trainingCounts(){
var training = {};
training.docCounts = documents;
training.docNotInCounts = {};
var count = 0;
for(var language in documents){
count += documents[language];
}
training.totalDocCount = count;
for(language in documents){
training.docNotInCounts[language] =
training.totalDocCount - documents[language];
}
return training;
}
function wordTotalCount(word){
var count = 0;
if(wordsTotal[word]){
count = wordsTotal[word];
}
return count;
}
function wordCountInLanguage(word,language){
var count = 0;
if(wordsPerLanguage[word]){
if (wordsPerLanguage[word][language]){
count = wordsPerLanguage[word][language];
}
}
return count;
}
var wordNotInLanguageCount = function (word, language) {
var total = 0;
for (var document in documents) {
if (document === language)
continue;
total += wordCountInLanguage(word, document);
}
return total;
};
function calculateProbability(word,language,training){
// probability that word shows up in a language
// e.g. the probability that "bonjour" shows up in a French document
// ----------------------------------------------------------
// YOUR CODE
// ----------------------------------------------------------
// probability that word is not in language
// ----------------------------------------------------------
// YOUR CODE
// ----------------------------------------------------------
// probability that document is in a "language" given that "word" is in it
// e.g. probability that document is french given that "bonjour" is in it
// http://en.wikipedia.org/w/index.php?title=Naive_Bayes_spam_filtering#Computing_the_probability_that_a_message_containing_a_given_word_is_spam
// ----------------------------------------------------------
// YOUR CODE
// ----------------------------------------------------------
// avoid 0 and 1 for later log calculations
if (probability === 0) probability = 0.01;
else if (probability === 1) probability = 0.99;
return probability;
}