snowball

Snowball stemmers for deno. These stemmers are based on the compiled JavaScript stemmers from the snowball project version 2.2.0.

Usage

EnglishStemmer

Provides the stem of the given word. Assumes that the input is lowercase.

import { assertStrictEquals } from "./test_deps.ts";
import { EnglishStemmer } from "https://deno.land/x/snowball/english_stemmer.ts";

const englishStemmer = new EnglishStemmer();

const stem = englishStemmer.stem("enthusiastically");

assertStrictEquals(stem, "enthusiast");

Here is an example with multiple words.

import { assertStrictEquals } from "./test_deps.ts";
import { EnglishStemmer } from "https://deno.land/x/snowball/english_stemmer.ts";

const sentence = "the quick brown fox jumped over the lazy dog";

const englishStemmer = new EnglishStemmer();

const stemmedSentence = sentence
  .match(/\b\w\w+\b/gu) // matches two or more word characters
  .map((token) => englishStemmer.stem(token))
  .join(" ");

assertStrictEquals(
  stemmedSentence,
  "the quick brown fox jump over the lazi dog",
);

RussianStemmer

Many languages are supported

import { assertStrictEquals } from "./test_deps.ts";
import { RussianStemmer } from "https://deno.land/x/snowball/russian_stemmer.ts";

const sentence = "обязательно выпейте свой овалтин";

const russianStemmer = new RussianStemmer();

const stemmedSentence = sentence
  .split(/\s+/u)
  .map((token) => russianStemmer.stem(token))
  .join(" ");

assertStrictEquals(
  stemmedSentence,
  "обязательн вып сво овалтин",
);

LanguageStemmers

There is an Object containing all available languages and stemmers defined in mod.ts.

import { assertStrictEquals } from "https://deno.land/[email protected]/testing/asserts.ts";
import { LanguageStemmers } from "https://deno.land/x/snowball/mod.ts";

const spanishStemmer = new LanguageStemmers["Spanish"]();

assertStrictEquals(
  spanishStemmer.stem("gracias"),
  "graci",
);

stopWords

Stop words generally provide little or no information. Some languages come with common stop words from the snowball-website. These can also be imported individually from the file containing the stopwords for that language. You should tokenize and stem these stop words the same way you do with your input text.

import { assert } from "https://deno.land/[email protected]/testing/asserts.ts";
import { EnglishStemmer } from "https://deno.land/x/snowball/english_stemmer.ts";

const englishStemmer = new EnglishStemmer();

assert(englishStemmer.stopWords.has("been"));

Supported Languages

Unless specified, there is only one stemmer available called LanguageStemmer which is exported from language_stemmer.ts and mod.ts. Replace language with the desired language respecting the hinted capitalization.

1. Arabic
2. Armenian
3. Basque
4. Catalan
5. Danish
6. Dutch
   1. DutchStemmer
   2. KraaijPohlmannStemmer
7. English
   1. EnglishStemmer - Porter 2 or snowball algorithm
   2. PorterStemmer - Porter 1 stemmer
   3. LovinsStemmer - The first published stemming algorithm
8. Finnish
9. French
10. German
    1. GermanStemmer
    2. German2Stemmer
11. Greek
12. Hindi
13. Hungarian
14. Indonesian
15. Irish
16. Italian
17. Lithuanian
18. Nepali
19. Norwegian
20. Protugese
21. Romanian
22. Russian
23. Serbian
24. Spanish
25. Swedish
26. Tamil
27. Turkish
28. Yiddish