A Ruby implementation of SMOG (Simple Measure of Gobbledygook) scoring for measuring text complexity.

smog.rb

#!/usr/bin/env ruby
#
# Calculates the SMOG (Simple Measure of Gobbledygook) score for a given
# piece of text. A CLI utility that could very easily be adapted into
# a library if I could be be bothered.
#
# More on SMOG: https://en.wikipedia.org/wiki/SMOG
#
# Author: Rob Miller <r@robm.me.uk>
#
# Usage:
#
#   $ ./smog path/to/file.txt
#   SMOG score: 15.34
#   Sentences: 14
#   Words: 263
#   Polysyllables: 64

class Smog
  def initialize(text)
    @text = text
  end

  def score
    (3.1291 + 1.043 * Math.sqrt(num_polysyllables * ( 30 / num_sentences.to_f ))).round(2)
  end

  def num_sentences
    sentences.length
  end

  def num_words
    words.length
  end

  def num_polysyllables
    polysyllables.length
  end

  private

  attr_reader :text

  def sentences
    @sentences ||= text.split(/\.|!|\?|\;/).reject { |s| s !~ /\w/ }
  end

  def words
    @words ||= text.split(/\s+|—|–/).reject { |w| w !~ /\w/i }.map { |w| w.gsub(/[\(),]/, "") }
  end

  def polysyllables
    @polysyllables ||= words.find_all { |word| Syllables.new(word).count >= 3 }
  end

  # A Ruby port of Greg Fast's Perl original, from the
  # Lingua::EN::Syllable package:
  # http://search.cpan.org/dist/Lingua-EN-Syllable/
  #
  # That original is copyright (c) 1999 by Greg Fast and distributed
  # under the GPL.
  class Syllables
    SUBTRACT = [
      /cial/,
      /tia/,
      /cius/,
      /cious/,
      /giu/,
      /ion/,
      /iou/,
      /sia$/,
      /.ely$/,
      /[^td]ed$/,
    ]

    ADD = [
      /ia/,
      /riet/,
      /dien/,
      /iu/,
      /io/,
      /ii/,
      /microor/,
      /[aeiouym]bl$/,
      /[aeiou]{3}/,
      /^mc/,
      /ism$/,
      /isms$/,
      /([^aeiouy])\1l$/,
      /[^l]lien/,
      /^coa[dglx]./,
      /[^gq]ua[^auieo]/,
      /dnt$/,
    ]

    def initialize(word)
      @word = word
    end

    def count
      word = @word.dup.downcase

      return 2 if word == "w"
      return 1 if word.length == 1

      word.gsub!("'", "")
      word.gsub!(/e$/, "")

      scrugg = word.split(/[^aeiouy]+/).reject { |s| s.nil? || s == "" }

      syl = 0

      SUBTRACT.each do |pattern|
        syl -= 1 if word =~ pattern
      end

      ADD.each do |pattern|
        syl += 1 if word =~ pattern
      end

      syl += scrugg.length

      syl = 1 if syl == 0

      syl
    end
  end
end

smog = Smog.new(File.read(ARGV[0]))

puts "SMOG score: #{smog.score}"
puts "Sentences: #{smog.num_sentences}"
puts "Words: #{smog.num_words}"
puts "Polysyllables: #{smog.num_polysyllables}"