How do I do word Stemming or Lemmatization?

Question

I've tried PorterStemmer and Snowball but both don't work on all words, missing some very common ones.

My test words are: "cats running ran cactus cactuses cacti community communities", and both get less than half right.

See also:

• Stemming algorithm that produces real words
• Stemming - code examples or open source projects?

Answer 1

Take a look at LemmaGen - open source library written in C# 3.0.

Results for your test words (http://lemmatise.ijs.si/Services)

• cats -> cat
• running
• ran -> run
• cactus
• cactuses -> cactus
• cacti -> cactus
• community
• communities -> community

Answer 2

If I may quote my answer to the question StompChicken mentioned:

The core issue here is that stemming algorithms operate on a phonetic basis with no actual understanding of the language they're working with.

As they have no understanding of the language and do not run from a dictionary of terms, they have no way of recognizing and responding appropriately to irregular cases, such as "run"/"ran".

If you need to handle irregular cases, you'll need to either choose a different approach or augment your stemming with your own custom dictionary of corrections to run after the stemmer has done its thing.

Answer 3

http://wordnet.princeton.edu/man/morph.3WN

For a lot of my projects, I prefer the lexicon-based WordNet lemmatizer over the more aggressive porter stemming.

http://wordnet.princeton.edu/links#PHP has a link to a PHP interface to the WN APIs.

Answer 4

In Java, i use tartargus-snowball to stemming words

Maven:

<dependency>
        <groupId>org.apache.lucene</groupId>
        <artifactId>lucene-snowball</artifactId>
        <version>3.0.3</version>
        <scope>test</scope>
</dependency>

Sample code:

SnowballProgram stemmer = new EnglishStemmer();
String[] words = new String[]{
    "testing",
    "skincare",
    "eyecare",
    "eye",
    "worked",
    "read"
};
for (String word : words) {
    stemmer.setCurrent(word);
    stemmer.stem();
    //debug
    logger.info("Origin: " + word + " > " + stemmer.getCurrent());// result: test, skincar, eyecar, eye, work, read
}

Answer 5

I tried your list of terms on this snowball demo site and the results look okay....

• cats -> cat
• running -> run
• ran -> ran
• cactus -> cactus
• cactuses -> cactus
• community -> communiti
• communities -> communiti

A stemmer is supposed to turn inflected forms of words down to some common root. It's not really a stemmer's job to make that root a 'proper' dictionary word. For that you need to look at morphological/orthographic analysers.

I think this question is about more or less the same thing, and Kaarel's answer to that question is where I took the second link from.

Answer 6

This looks interesting: MIT Java WordnetStemmer: http://projects.csail.mit.edu/jwi/api/edu/mit/jwi/morph/WordnetStemmer.html