basic-sentiment.rb

#############################################################################
# Filename: basic-sentiment.rb
# Copyright: Christopher MacLellan 2010
# Description: This code adds functions to the string class for calculating
#              the sentivalue of strings. It is not called directly by the
#              tweet-search-sentiment.rb program but is included for possible 
#              future use.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#############################################################################


class String
  @@sentihash = {}

  #####################################################################
  # Function that returns the sentiment value for a given string.
  # This value is the sum of the sentiment values of each of the words.
  # Stop words are NOT removed.
  #
  # return:float -- sentiment value of the current string
  #####################################################################
  def get_sentiment
    sentiment_total = 0.0

    #tokenize the string
    tokens = self.split
    
    for token in tokens do
      sentiment_value = @@sentihash[token]
      
      if sentiment_value
        
        # for debugging purposes
        #puts "#{token} => #{sentiment_value}"
        
        sentiment_total += sentiment_value
      end
    end

    return sentiment_total

  end
  
  #####################################################################
  # load the specified sentiment file into a hash
  #
  # filename:string -- name of file to load
  # sentihash:hash -- hash to load data into
  # return:hash -- hash with data loaded
  #####################################################################
  def load_senti_file (filename)
    # load the word file
    file = File.new(filename)
    while (line = file.gets)
      parsedline = line.chomp.split("\t")
      sentiscore = parsedline[0]
      text = parsedline[1]
      @@sentihash[text] = sentiscore.to_f
    end
    file.close
  end
  
end