Class: Text::WhiteSimilarity

Inherits:
Object
  • Object
show all
Defined in:
lib/text/white_similarity.rb

Overview

Ruby implementation of the string similarity described by Simon White at: www.catalysoft.com/articles/StrikeAMatch.html

                     2 * |pairs(s1) INTERSECT pairs(s2)|
similarity(s1, s2) = -----------------------------------
                         |pairs(s1)| + |pairs(s2)|

e.g.

                                          2 * |{FR, NC}|
similarity(FRANCE, FRENCH) = ---------------------------------------
                             |{FR,RA,AN,NC,CE}| + |{FR,RE,EN,NC,CH}|

                           = (2 * 2) / (5 + 5)

                           = 0.4

WhiteSimilarity.new.similarity("FRANCE", "FRENCH")

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ WhiteSimilarity

Returns a new instance of WhiteSimilarity.



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# File 'lib/text/white_similarity.rb', line 32

def initialize
  @word_letter_pairs = {}
end

Class Method Details

.similarity(str1, str2) ⇒ Object 



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# File 'lib/text/white_similarity.rb', line 28

def self.similarity(str1, str2)
  new.similarity(str1, str2)
end

Instance Method Details

#similarity(str1, str2) ⇒ Object 



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# File 'lib/text/white_similarity.rb', line 36

def similarity(str1, str2)
  pairs1 = word_letter_pairs(str1)
  pairs2 = word_letter_pairs(str2).dup

  union = pairs1.length + pairs2.length

  intersection = 0
  pairs1.each do |pair1|
    if index = pairs2.index(pair1)
      intersection += 1
      pairs2.delete_at(index)
    end
  end

  (2.0 * intersection) / union
end