Ruby module that converts a word to its approximate root form with the Porter stemmer. For example, observing and observation reduce to observ.
Ruby
Latest commit eb83051 Jan 24, 2012 @raypereda Merge pull request #1 from arbox/master
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README.rdoc

Stemmify

Description

This is a Rails gem for reducing words to their roots. For example, all the following words to are stemmed to “observ”, which is not a real word in this case: observance observances observancy observant observants observation observe observed observer observers observing observingly

The algorithm used here is based on the Porter stemmer. You can read more about Martin Porter's stemmer at

tartarus.org/~martin/PorterStemmer/

Martin Porter explains:

The Porter stemming algorithm (or ‘Porter stemmer’) is a process for removing the commoner morphological and inflexional endings from words in English. Its main use is as part of a term normalisation process that is usually done when setting up Information Retrieval systems.

Install

$ sudo gem install stemmify

or

$ gem install stemmify

Note that while the source code is hosted on github, the actual gem is hosted on RubyGem.org.

Usage

Let's say you are building some sort of search tool. You want searches for “observations” and “observer” to all bring up the same items. When you are building you index, you can map all the words to their roots using the stem method.

Here's an example usage:

require 'stemmify'
print("observations".stem) # ==> "observ"

You can use stemmify as a command line tool:

$ stem input_file.txt
$ printf "I\nwalked\nin\nthe\nforest\n.\n" | stem

Both the file based input and the input taken from the stdin should be tokenized, i.e. provide one token per line, tokens should be delimeted e.g. by a new line feed.

For tokenization consider using a tokenizer, for instance the tokenizer gem.

Test Suite

This test is based on the sample input and output text from Martin Porter website. It includes 23532 test words and their expected stem results. To run the test, just type

rake test

Thanks

Dave Thomas from pragprog.com made speed improvements to this code before it was packaged as a gem.

License

Copyright © 2011 Ray Pereda

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.