natural

"Natural" is a general natural language facility for nodejs. Tokenizing, stemming, classification, phonetics, tf-idf, WordNet, string similarity, and some inflections are currently supported.

It's still in the early stages, so we're very interested in bug reports, contributions and the like.

Note that many algorithms from Rob Ellis's node-nltools are being merged into this project and will be maintained from here onward.

At the moment, most of the algorithms are English-specific, but in the long-term, some diversity will be in order. Thanks to Polyakov Vladimir, Russian stemming has been added!, Thanks to David Przybilla, Spanish stemming has been added!.

Aside from this README, the only documentation is this DZone article and here on my blog, which is a bit older.

Installation

If you're just looking to use natural without your own node application, you can install via NPM like so:

npm install natural

If you're interested in contributing to natural, or just hacking on it, then by all means fork away!

Tokenizers

Word, Regexp, and Treebank tokenizers are provided for breaking text up into arrays of tokens:

var natural = require('natural'),
  tokenizer = new natural.WordTokenizer();
console.log(tokenizer.tokenize("your dog has fleas."));
// [ 'your', 'dog', 'has', 'fleas' ]

The other tokenizers follow a similar pattern:

tokenizer = new natural.TreebankWordTokenizer();
console.log(tokenizer.tokenize("my dog hasn't any fleas."));
// [ 'my', 'dog', 'has', 'n\'t', 'any', 'fleas', '.' ]

tokenizer = new natural.RegexpTokenizer({pattern: /\-/});
console.log(tokenizer.tokenize("flea-dog"));
// [ 'flea', 'dog' ]

tokenizer = new natural.WordPunctTokenizer();
console.log(tokenizer.tokenize("my dog hasn't any fleas."));
// [ 'my',  'dog',  'hasn',  '\'',  't',  'any',  'fleas',  '.' ]

String Distance

Natural provides an implementation of the Jaro–Winkler string distance measuring algorithm. This will return a number between 0 and 1 which tells how closely the strings match (0 = not at all, 1 = exact match):

var natural = require('natural');
console.log(natural.JaroWinklerDistance("dixon","dicksonx"))
console.log(natural.JaroWinklerDistance('not', 'same'));

Output:

0.7466666666666666
0

Natural also offers support for Levenshtein distances:

var natural = require('natural');
console.log(natural.LevenshteinDistance("ones","onez"));
console.log(natural.LevenshteinDistance('one', 'one'));

Output:

1
0

The cost of the three edit operations are modifiable for Levenshtein:

console.log(natural.LevenshteinDistance("ones","onez", {
    insertion_cost: 1,
    deletion_cost: 1,
    substitution_cost: 1
}));

Output:

And Dice's co-efficient:

var natural = require('natural');
console.log(natural.DiceCoefficient('thing', 'thing'));
console.log(natural.DiceCoefficient('not', 'same'));

Output:

1
0

Stemmers

Currently stemming is supported via the Porter and Lancaster (Paice/Husk) algorithms.

var natural = require('natural');

This example uses a Porter stemmer. "word" is returned.

console.log(natural.PorterStemmer.stem("words")); // stem a single word

in Russian:

console.log(natural.PorterStemmerRu.stem("падший"));

in Spanish:

console.log(natural.PorterStemmerEs.stem("jugaría"));

attach() patches stem() and tokenizeAndStem() to String as a shortcut to PorterStemmer.stem(token). tokenizeAndStem() breaks text up into single words and returns an array of stemmed tokens.

natural.PorterStemmer.attach();
console.log("i am waking up to the sounds of chainsaws".tokenizeAndStem());
console.log("chainsaws".stem());

the same thing can be done with a Lancaster stemmer:

natural.LancasterStemmer.attach();
console.log("i am waking up to the sounds of chainsaws".tokenizeAndStem());
console.log("chainsaws".stem());

Classifiers

Two classifiers are currently supported, Naive Bayes and logistic regression. The following examples use the BayesClassifier class, but the LogisticRegressionClassifier class could be substituted instead.

var natural = require('natural'),
  classifier = new natural.BayesClassifier();

You can train the classifier on sample text. It will use reasonable defaults to tokenize and stem the text.

classifier.addDocument('i am long qqqq', 'buy');
classifier.addDocument('buy the q\'s', 'buy');
classifier.addDocument('short gold', 'sell');
classifier.addDocument('sell gold', 'sell');

classifier.train();

Outputs "sell"

console.log(classifier.classify('i am short silver'));

Outputs "buy"

console.log(classifier.classify('i am long copper'));

You have access to the set of matched classes and the associated value from the classifier.

Outputs:

[ { label: 'buy', value: 0.39999999999999997 },
  { label: 'sell', value: 0.19999999999999998 } ]

From this:

console.log(classifier.getClassifications('i am long copper'));

The classifier can also be trained with and can classify arrays of tokens, strings, or any mixture of the two. Arrays let you use entirely custom data with your own tokenization/stemming, if you choose to implement it.

classifier.addDocument(['sell', 'gold'], 'sell');

The training process can be monitored by subscribing to the event trainedWithDocument that's emitted by the classifier, this event's emitted each time a document is finished being trained against:

classifier.events.on('trainedWithDocument', function (obj) {
   console.log(obj);
   /* {
   *   total: 23 // There are 23 total documents being trained against
   *   index: 12 // The index/number of the document that's just been trained against
   *   doc: {...} // The document that has just been indexed
   *  }
   */ 
});

A classifier can also be persisted and recalled so you can reuse a training

classifier.save('classifier.json', function(err, classifier) {
    // the classifier is saved to the classifier.json file!
});

To recall from the classifier.json saved above:

natural.BayesClassifier.load('classifier.json', null, function(err, classifier) {
    console.log(classifier.classify('long SUNW'));
    console.log(classifier.classify('short SUNW'));
});

A classifier can also be serialized and deserialized like so:

var classifier = new natural.BayesClassifier();
classifier.addDocument(['sell', 'gold'], 'sell');
classifier.addDocument(['buy', 'silver'], 'buy');

// serialize
var raw = JSON.stringify(classifier);
// deserialize
var restoredClassifier = natural.BayesClassifier.restore(JSON.parse(raw));
console.log(restoredClassifier.classify('i should sell that'));

Phonetics

Phonetic matching (sounds-like) matching can be done with the SoundEx, Metaphone or DoubleMetaphone algorithms

var natural = require('natural'),
    metaphone = natural.Metaphone, soundEx = natural.SoundEx;

var wordA = 'phonetics';
var wordB = 'fonetix';

To test the two words to see if they sound alike:

if(metaphone.compare(wordA, wordB))
    console.log('they sound alike!');

The raw phonetics are obtained with process():

console.log(metaphone.process('phonetics'));

A maximum code length can be supplied:

console.log(metaphone.process('phonetics', 3));

DoubleMetaphone deals with two encodings returned in an array. This feature is experimental and subject to change:

var natural = require('natural'),
  dm = natural.DoubleMetaphone;

var encodings = dm.process('Matrix');
console.log(encodings[0]);
console.log(encodings[1]);

Attaching will patch String with useful methods:

metaphone.attach();

soundsLike is essentially a shortcut to Metaphone.compare:

if(wordA.soundsLike(wordB))
    console.log('they sound alike!');

The raw phonetics are obtained with phonetics():

console.log('phonetics'.phonetics());

Full text strings can be tokenized into arrays of phonetics (much like how tokenization-to-arrays works for stemmers):

console.log('phonetics rock'.tokenizeAndPhoneticize());

Same module operations applied with SoundEx:

if(soundEx.compare(wordA, wordB))
    console.log('they sound alike!');

The same String patches apply with soundEx:

soundEx.attach();

if(wordA.soundsLike(wordB))
    console.log('they sound alike!');

console.log('phonetics'.phonetics());

Inflectors

Nouns

Nouns can be pluralized/singularized with a NounInflector:

var natural = require('natural'),
nounInflector = new natural.NounInflector();

To pluralize a word (outputs "radii"):

console.log(nounInflector.pluralize('radius'));

To singularize a word (outputs "beer"):

console.log(nounInflector.singularize('beers'));

Like many of the other features, String can be patched to perform the operations directly. The "Noun" suffix on the methods is necessary, as verbs will be supported in the future.

nounInflector.attach();
console.log('radius'.pluralizeNoun());
console.log('beers'.singularizeNoun());

Numbers

Numbers can be counted with a CountInflector:

var countInflector = natural.CountInflector;

Outputs "1st":

console.log(countInflector.nth(1));

Outputs "111th":

console.log(countInflector.nth(111));

Present Tense Verbs

Present Tense Verbs can be pluralized/singularized with a PresentVerbInflector. This feature is still experimental as of 0.0.42, so use with caution, and please provide feedback.

var verbInflector = new natural.PresentVerbInflector();

Outputs "becomes":

console.log(verbInflector.singularize('become'));

Outputs "become":

console.log(verbInflector.pluralize('becomes'));

Like many other natural modules, attach() can be used to patch strings with handy methods.

verbInflector.attach();
console.log('walk'.singularizePresentVerb());
console.log('walks'.pluralizePresentVerb());

N-Grams

n-grams can be obtained for either arrays or strings (which will be tokenized for you):

var NGrams = natural.NGrams;

bigrams

console.log(NGrams.bigrams('some words here'));
console.log(NGrams.bigrams(['some',  'words',  'here']));

Both of the above output: [ [ 'some', 'words' ], [ 'words', 'here' ] ]

trigrams

console.log(NGrams.trigrams('some other words here'));
console.log(NGrams.trigrams(['some',  'other', 'words',  'here']));

Both of the above output: [ [ 'some', 'other', 'words' ], [ 'other', 'words', 'here' ] ]

arbitrary n-grams

console.log(NGrams.ngrams('some other words here for you', 4));
console.log(NGrams.ngrams(['some', 'other', 'words', 'here', 'for',
    'you'], 4));

The above outputs: [ [ 'some', 'other', 'words', 'here' ], [ 'other', 'words', 'here', 'for' ], [ 'words', 'here', 'for', 'you' ] ]

padding

n-grams can also be returned with left or right padding by passing a start and/or end symbol to the bigrams, trigrams or ngrams.

console.log(NGrams.ngrams('some other words here for you', 4, '[start]', '[end]'));

The above will output:

[ [ '[start]', '[start]', '[start]', 'some' ],
  [ '[start]', '[start]', 'some', 'other' ],
  [ '[start]', 'some', 'other', 'words' ],
  [ 'some', 'other', 'words', 'here' ],
  [ 'other', 'words', 'here', 'for' ],
  [ 'words', 'here', 'for', 'you' ],
  [ 'here', 'for', 'you', '[end]' ],
  [ 'for', 'you', '[end]', '[end]' ],
  [ 'you', '[end]', '[end]', '[end]' ] ]

For only end symbols, pass null for the start symbol, for instance:

console.log(NGrams.ngrams('some other words here for you', 4, null, '[end]'));

Will output:

[ [ 'some', 'other', 'words', 'here' ],
  [ 'other', 'words', 'here', 'for' ],
  [ 'words', 'here', 'for', 'you' ],
  [ 'here', 'for', 'you', '[end]' ],
  [ 'for', 'you', '[end]', '[end]' ],
  [ 'you', '[end]', '[end]', '[end]' ] ]

NGramsZH

For Chinese like languages, you can use NGramsZH to do a n-gram, and all apis are the same:

var NGramsZH = natural.NGramsZH;
console.log(NGramsZH.bigrams('中文测试'));
console.log(NGramsZH.bigrams(['中',  '文',  '测', '试']));
console.log(NGramsZH.trigrams('中文测试'));
console.log(NGramsZH.trigrams(['中',  '文', '测',  '试']));
console.log(NGramsZH.ngrams('一个中文测试', 4));
console.log(NGramsZH.ngrams(['一', '个', '中', '文', '测',
    '试'], 4));

tf-idf

Term Frequency–Inverse Document Frequency (tf-idf) is implemented to determine how important a word (or words) is to a document relative to a corpus. The following example will add four documents to a corpus and determine the weight of the word "node" and then the weight of the word "ruby" in each document.

var natural = require('natural'),
    TfIdf = natural.TfIdf,
    tfidf = new TfIdf();

tfidf.addDocument('this document is about node.');
tfidf.addDocument('this document is about ruby.');
tfidf.addDocument('this document is about ruby and node.');
tfidf.addDocument('this document is about node. it has node examples');

console.log('node --------------------------------');
tfidf.tfidfs('node', function(i, measure) {
    console.log('document #' + i + ' is ' + measure);
});

console.log('ruby --------------------------------');
tfidf.tfidfs('ruby', function(i, measure) {
    console.log('document #' + i + ' is ' + measure);
});

The above outputs:

node --------------------------------
document #0 is 1.4469189829363254
document #1 is 0
document #2 is 1.4469189829363254
document #3 is 2.8938379658726507
ruby --------------------------------
document #0 is 0
document #1 is 1.466337068793427
document #2 is 1.466337068793427
document #3 is 0

This approach can also be applied to individual documents.

The following example measures the term "node" in the first and second documents.

console.log(tfidf.tfidf('node', 0));
console.log(tfidf.tfidf('node', 1));

A TfIdf instance can also load documents from files on disk.

var tfidf = new TfIdf();
tfidf.addFileSync('data_files/one.txt');
tfidf.addFileSync('data_files/two.txt');

Multiple terms can be measured as well, with their weights being added into a single measure value. The following example determines that the last document is the most relevant to the words "node" and "ruby".

var natural = require('natural'),
    TfIdf = natural.TfIdf,
    tfidf = new TfIdf();

tfidf.addDocument('this document is about node.');
tfidf.addDocument('this document is about ruby.');
tfidf.addDocument('this document is about ruby and node.');

tfidf.tfidfs('node ruby', function(i, measure) {
    console.log('document #' + i + ' is ' + measure);
});

The above outputs:

document #0 is 1.2039728043259361
document #1 is 1.2039728043259361
document #2 is 2.4079456086518722

The examples above all use strings, which case natural to automatically tokenize the input. If you wish to perform your own tokenization or other kinds of processing, you can do so, then pass in the resultant arrays later. This approach allows you to bypass natural's default preprocessing.

var natural = require('natural'),
    TfIdf = natural.TfIdf,
    tfidf = new TfIdf();

tfidf.addDocument(['document', 'about', 'node']);
tfidf.addDocument(['document', 'about', 'ruby']);
tfidf.addDocument(['document', 'about', 'ruby', 'node']);
tfidf.addDocument(['document', 'about', 'node', 'node', 'examples']);

tfidf.tfidfs(['node', 'ruby'], function(i, measure) {
    console.log('document #' + i + ' is ' + measure);
});

It's possible to retrieve a list of all terms in a document, sorted by their importance.

tfidf.listTerms(0 /*document index*/).forEach(function(item) {
    console.log(item.term + ': ' + item.tfidf);
});

A TfIdf instance can also be serialized and deserialized for save and recall.

var tfidf = new TfIdf();
tfidf.addDocument('document one', 'un');
tfidf.addDocument('document Two', 'deux');
var s = JSON.stringify(tfidf);
// save "s" to disk, database or otherwise

// assuming you pulled "s" back out of storage.
var tfidf = new TfIdf(JSON.parse(s));

Tries

Tries are a very efficient data structure used for prefix-based searches. Natural comes packaged with a basic Trie implementation which can support match collection along a path, existence search and prefix search.

Building The Trie

You need to add words to build up the dictionary of the Trie, this is an example of basic Trie set up:

var natural = require('natural'),
    Trie = natural.Trie;

var trie = new Trie();

// Add one string at a time
trie.addString("test");

// Or add many strings
trie.addStrings(["string1", "string2", "string3"]);

Searching

Contains

The most basic operation on a Trie is to see if a search string is marked as a word in the Trie.

console.log(trie.contains("test")); // true
console.log(trie.contains("asdf")); // false

Find Prefix

The find prefix search will find the longest prefix that is identified as a word in the trie. It will also return the remaining portion of the string which it was not able to match.

console.log(trie.findPrefix("tester"));     // ['test', 'er']
console.log(trie.findPrefix("string4"));    // [null, '4']
console.log(trie.findPrefix("string3"));    // ['string3', '']

All Prefixes on Path

This search will return all prefix matches along the search string path.

trie.addString("tes");
trie.addString("est");
console.log(trie.findMatchesOnPath("tester")); // ['tes', 'test'];

All Keys with Prefix

This search will return all of the words in the Trie with the given prefix, or [ ] if not found.

console.log(trie.keysWithPrefix("string")); // ["string1", "string2", "string3"]

Case-Sensitivity

By default the trie is case-sensitive, you can use it in case-_in_sensitive mode by passing false to the Trie constructor.

trie.contains("TEST"); // false

var ciTrie = new Trie(false);
ciTrie.addString("test");
ciTrie.contains("TEsT"); // true

In the case of the searches which return strings, all strings returned will be in lower case if you are in case-_in_sensitive mode.

EdgeWeightedDigraph

EdgeWeightedDigraph represents a digraph, you can add an edge, get the number vertexes, edges, get all edges and use toString to print the Digraph.

initialize a digraph:

var EdgeWeightedDigraph = natural.EdgeWeightedDigraph;
var digraph = new EdgeWeightedDigraph();
digraph.add(5,4,0.35);
digraph.add(5,1,0.32);
digraph.add(1,3,0.29);
digraph.add(6,2,0.40);
digraph.add(3,6,0.52);
digraph.add(6,4,0.93);

the api used is: add(from, to, weight).

get the number of vertexes:

console.log(digraph.v());

you will get 5.

get the number of edges:

console.log(digraph.e());

you will get 5.

ShortestPathTree

ShortestPathTree represents a data type for solving the single-source shortest paths problem in edge-weighted directed acyclic graphs (DAGs). The edge weights can be positive, negative, or zero. There are three APIs: getDistTo(vertex), hasPathTo(vertex), pathTo(vertex).

var ShortestPathTree = natural.ShortestPathTree;
var spt = new ShortestPathTree(digraph, 5);

digraph is an instance of EdgeWeightedDigraph, the second param is the start vertex of DAG.

getDistTo(vertex)

Will return the dist to vertex.

console.log(spt.getDistTo(4));

the output will be: 0.35

hasDistTo(vertex)

console.log(spt.hasDistTo(4));
console.log(spt.hasDistTo(5));

output will be:

true
false

pathTo(vertex)

this will return a shortest path:

console.log(spt.pathTo(4));

output will be:

[5, 4]

LongestPathTree

LongestPathTree represents a data type for solving the single-source shortest paths problem in edge-weighted directed acyclic graphs (DAGs). The edge weights can be positive, negative, or zero. There are three APIs same as ShortestPathTree: getDistTo(vertex), hasPathTo(vertex), pathTo(vertex).

var ShortestPathTree = natural.ShortestPathTree;
var spt = new ShortestPathTree(digraph, 5);

digraph is an instance of EdgeWeightedDigraph, the second param is the start vertex of DAG.

getDistTo(vertex)

Will return the dist to vertex.

console.log(spt.getDistTo(4));

the output will be: 2.06

hasDistTo(vertex)

console.log(spt.hasDistTo(4));
console.log(spt.hasDistTo(5));

output will be:

true
false

pathTo(vertex)

this will return a shortest path:

console.log(spt.pathTo(4));

output will be:

[5, 1, 3, 6, 4]

WordNet

One of the newest and most experimental features in natural is WordNet integration. Here's an example of using natural to look up definitions of the word node. To use the WordNet module, first install the WordNet database files using wordnet-db:

npm install wordnet-db

Keep in mind that the WordNet integration is to be considered experimental at this point, and not production-ready. The API is also subject to change. For an implementation with vastly increased performance, as well as a command-line interface, see wordpos.

Here's an example of looking up definitions for the word "node".

var wordnet = new natural.WordNet();

wordnet.lookup('node', function(results) {
    results.forEach(function(result) {
        console.log('------------------------------------');
        console.log(result.synsetOffset);
        console.log(result.pos);
        console.log(result.lemma);
        console.log(result.synonyms);
        console.log(result.pos);
        console.log(result.gloss);
    });
});

Given a synset offset and a part of speech, a definition can be looked up directly.

var wordnet = new natural.WordNet();

wordnet.get(4424418, 'n', function(result) {
    console.log('------------------------------------');
    console.log(result.lemma);
    console.log(result.pos);
    console.log(result.gloss);
    console.log(result.synonyms);
});

If you have manually downloaded the WordNet database files, you can pass the folder to the constructor:

var wordnet = new natural.WordNet('/my/wordnet/dict');

As of v0.1.11, WordNet data files are no longer automatically downloaded.

Princeton University "About WordNet." WordNet. Princeton University. 2010. http://wordnet.princeton.edu

Spellcheck

A probabilistic spellchecker based on http://norvig.com/spell-correct.html

This is best constructed with an array of tokens from a corpus, but a simple list of words from a dictionary will work.

var corpus = ['something', 'soothing'];
var spellcheck = new Spellcheck(corpus);

It uses the trie datastructure for fast boolean lookup of a word

spellcheck.isCorrect('cat'); // false

It suggests corrections (sorted by probability in descending order) that are up to a maximum edit distance away from the input word. According to Norvig, a max distance of 1 will cover 80% to 95% of spelling mistakes. After a distance of 2, it becomes very slow.

spellcheck.getCorrections('soemthing', 1); // ['something']
spellcheck.getCorrections('soemthing', 2); // ['something', 'soothing']

POS Tagger

This is a part-of-speech tagger based on Eric Brill's transformational algorithm. Transformation rules are specified in external files.

Usage

var Tagger = require("./lib/natural").BrillPOSTagger;

var base_folder = "some_path/lib/natural/brill_pos_tagger";
var rules_file = base_folder + "/data/tr_from_posjs.txt";
var lexicon_file = base_folder + "/data/lexicon_from_posjs.json";
var default_category = 'N';

var tagger = new Tagger(lexicon_file, rules_file, default_category, function(error) {
  if (error) {
    console.log(error);
  }
  else {
    var sentence = ["I", "see", "the", "man", "with", "the", "telescope"];
    console.log(JSON.stringify(tagger.tag(sentence)));
  }
});

Lexicon

The lexicon is either a JSON file that has the following structure:

{
  "word1": ["cat1"],
  "word2": ["cat2", "cat3"],
  ...
}

or a text file:

word1 cat1 cat2
word2 cat3
...

Words may have multiple categories in the lexicon file. The tagger uses only the first category specified.

Specifying transformation rules

Transformation rules are specified as follows:

OLD_CAT NEW_CAT PREDICATE PARAMETER

This means that if the category of the current position is OLD_CAT and the predicate is true, the category is replaced by NEW_CAT. The predicate may use the parameter in different ways: sometimes the parameter is used for specifying the outcome of the predicate:

NN CD CURRENT-WORD-IS-NUMBER YES

This means that if the outcome of predicate CURRENT-WORD-IS-NUMBER is YES, the category is replaced by CD. The parameter can also be used to check the category of a word in the sentence:

VBD NN PREV-TAG DT

Here the category of the previous word must be DT for the rule to be applied.

Algorithm

The tagger applies transformation rules that may change the category of words. The input sentence must be split into words which are assigned with categories. The tagged sentence is then processed from left to right. At each step all rules are applied once; rules are applied in the order in which they are specified. Algorithm:

function(sentence) {
  var tagged_sentence = new Array(sentence.length);

  // snip

  // Apply transformation rules
  for (var i = 0, size = sentence.length; i < size; i++) {
    this.transformation_rules.forEach(function(rule) {
      rule.apply(tagged_sentence, i);
    });
  }
  return(tagged_sentence);
}

Adding a predicate

Predicates are defined in module lib/Predicate.js. In that file a function must be created that serves as predicate. A predicate accepts a tagged sentence, the current position in the sentence that should be tagged, and the outcome(s) of the predicate. An example of a predicate that checks the category of the current word:

function current_word_is_tag(tagged_sentence, i, parameter) {
  return(tagged_sentence[i][0] === parameter);
}

Some predicates accept two parameters. Next step is to map a keyword to this predicate so that it can be used in the transformation rules. The mapping is also defined in lib/Predicate.js:

var predicates = {
  "CURRENT-WORD-IS-TAG": current_word_is_tag,
  "PREV-WORD-IS-CAP": prev_word_is_cap
}

Acknowledgements and References

Part of speech tagger by Percy Wegmann, https://code.google.com/p/jspos/
Node.js version of jspos: https://github.com/neopunisher/pos-js
A simple rule-based part of speech tagger, Eric Brill, Published in: Proceeding ANLC '92 Proceedings of the third conference on Applied natural language processing, Pages 152-155. http://dl.acm.org/citation.cfm?id=974526

Development

When developing, please:

Write unit tests
Make sure your unit tests pass

The current configuration of the unit tests requires the following environment variable to be set:

export NODE_PATH=.

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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Name		Name	Last commit message	Last commit date
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benchmarks		benchmarks
examples		examples
io_spec		io_spec
lib/natural		lib/natural
spec		spec
.editorconfig		.editorconfig
.gitignore		.gitignore
.npmignore		.npmignore
.travis.yml		.travis.yml
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE.txt		LICENSE.txt
Makefile		Makefile
README.md		README.md
index.js		index.js
package.json		package.json

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natural

TABLE OF CONTENTS

Installation

Tokenizers

String Distance

Stemmers

Classifiers

Phonetics

Inflectors

Nouns

Numbers

Present Tense Verbs

N-Grams

bigrams

trigrams

arbitrary n-grams

padding

NGramsZH

tf-idf

Tries

Building The Trie

Searching

Contains

Find Prefix

All Prefixes on Path

All Keys with Prefix

Case-Sensitivity

EdgeWeightedDigraph

ShortestPathTree

getDistTo(vertex)

hasDistTo(vertex)

pathTo(vertex)

LongestPathTree

getDistTo(vertex)

hasDistTo(vertex)

pathTo(vertex)

WordNet

Spellcheck

POS Tagger

Usage

Lexicon

Specifying transformation rules

Algorithm

Adding a predicate

Acknowledgements and References

Development

License

WordNet License

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