My version of word_hash.rb I use for the classifier(https://github.com/cardmagic/classifier). It does not remove stop words, nor does it stem words. It also adds bi-grams to the bag of words(lines 21-28). This file lets the classifier look at the corpus more holistically, acknowledging that a corpus is not necessarily a bag of words, but that wo…

word_hash.rb

# Author::    Lucas Carlson  (mailto:lucas@rufy.com)
# Copyright:: Copyright (c) 2005 Lucas Carlson
# License::   LGPL

# These are extensions to the String class to provide convenience 
# methods for the Classifier package.
class String
  
  # Removes common punctuation symbols, returning a new string. 
  # E.g.,
  #   "Hello (greeting's), with {braces} < >...?".without_punctuation
  #   => "Hello  greetings   with  braces         "
  def without_punctuation
    tr( ',?.!;:"@#$%^&*()_=+[]{}\|<>/`~', " " ) .tr( "'\-", "")
  end
  
  # Return a Hash of strings => ints. Each word in the string is stemmed,
  # interned, and indexes to its frequency in the document.  
  def word_hash
	  #word_hash_for_words(gsub(/[^\w\s]/,"").split + gsub(/[\w]/," ").split)
	  ls = self.split
	  len = ls.length
	  x=0
	  arr = []
	  while(x<len-1) do
	    arr<<(ls[x]+" "+ls[x+1])
	    x+=1;
    end
    word_hash_for_words(arr+gsub(/[^\w\s]/,"").split + gsub(/[\w]/," ").split)
	end

	# Return a word hash without extra punctuation or short symbols, just stemmed words
	def clean_word_hash
		word_hash_for_words gsub(/[^\w\s]/,"").split
	end
	
	private
	
	def word_hash_for_words(words)
		d = Hash.new
		words.each do |word|
			word.downcase! if word =~ /[\w]+/
			key = word.intern
		#	key = word.stem.intern
			if word =~ /[^\w]/ || ! CORPUS_SKIP_WORDS.include?(word) && word.length > 2
				d[key] ||= 0
				d[key] += 1
			end
		end
		return d
	end
	CORPUS_SKIP_WORDS = [
=begin
      "a",
      "again",
      "all",
      "along",
      "are",
      "also",
      "an",
      "and",
      "as",
      "at",
      "but",
      "by",
      "came",
      "can",
      "cant",
      "couldnt",
      "did",
      "didn",
      "didnt",
      "do",
      "doesnt",
      "dont",
      "ever",
      "first",
      "from",
      "have",
      "her",
      "here",
      "him",
      "how",
      "i",
      "if",
      "in",
      "into",
      "is",
      "isnt",
      "it",
      "itll",
      "just",
      "last",
      "least",
      "like",
      "most",
      "my",
      "new",
      "no",
      "not",
      "now",
      "of",
      "on",
      "or",
      "should",
      "sinc",
      "so",
      "some",
      "th",
      "than",
      "this",
      "that",
      "the",
      "their",
      "then",
      "those",
      "to",
      "told",
      "too",
      "true",
      "try",
      "until",
      "url",
      "us",
      "were",
      "when",
      "whether",
      "while",
      "with",
      "within",
      "yes",
      "you",
      "youll",
=end

      ]
end