"Natural" is a general natural language facility for node.js. 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.
I'm having trouble devoting the time necessary to maintain natural. While I'm certainly not leaving the project I'd like someone to take over the day-to-day maintenance of dealing with issues, pull requests and driving the direction of the software moving forward. Please contact [email protected] if you're interested!
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!
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 flees."));
// [ 'your', 'dog', 'has', 'flees' ]
The other tokenizers follow a similar pattern:
tokenizer = new natural.TreebankWordTokenizer();
console.log(tokenizer.tokenize("my dog hasn't any flees."));
// [ 'my', 'dog', 'has', 'n\'t', 'any', 'flees', '.' ]
tokenizer = new natural.RegexpTokenizer({pattern: /\-/});
console.log(tokenizer.tokenize("flee-dog"));
// [ 'flee', 'dog' ]
tokenizer = new natural.WordPunctTokenizer();
console.log(tokenizer.tokenize("my dog hasn't any flees."));
// [ 'my', 'dog', 'hasn', '\'', 't', 'any', 'flees', '.' ]
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:
1
And Dice's co-efficient:
var natural = require('natural');
console.log(natural.DiceCoefficient('thing', 'thing'));
console.log(natural.DiceCoefficient('not', 'same'));
Output:
1
0
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());
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: 'sell', value: 0.39999999999999997 },
{ label: 'buy', 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'));
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());
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 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 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 can be obtained for either arrays or strings (which will be tokenized for you):
var NGrams = natural.NGrams;
console.log(NGrams.bigrams('some words here'));
console.log(NGrams.bigrams(['some', 'words', 'here']));
Both of the above output: [ [ 'some', 'words' ], [ 'words', 'here' ] ]
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' ] ]
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' ] ]
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 relevent 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 deserialzed 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 are a very efficient data structure used for prefix-based searches. Natural comes packaged with a basic Trie implementation wich can support match collection along a path, existance search and prefix search.
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"]);
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
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', '']
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'];
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.
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 the WNdb module:
npm install WNdb
(For node < v0.6, please use 'npm install [email protected]')
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.
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
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=.
Copyright (c) 2011, 2012 Chris Umbel, Rob Ellis, Russell Mull
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.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
This license is available as the file LICENSE in any downloaded version of WordNet. WordNet 3.0 license: (Download)
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