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@otobrglez
Last active April 2, 2024 17:51
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Simple recommendation system written in Ruby based on Jaccard index.
# Simple Recommendation Engine in Ruby
# Visit: http://otobrglez.opalab.com
# Author: Oto Brglez <otobrglez@gmail.com>
class Book < Struct.new(:title)
def words
@words ||= self.title.gsub(/[a-zA-Z]{3,}/).map(&:downcase).uniq.sort
end
end
class BookRecommender
def initialize book, books
@book, @books = book, books
end
def recommendations
@books.map! do |this_book|
this_book.define_singleton_method(:jaccard_index) do @jaccard_index; end
this_book.define_singleton_method("jaccard_index=") do |index|
@jaccard_index = index || 0.0
end
intersection = (@book.words & this_book.words).size
union = (@book.words | this_book.words).size
this_book.jaccard_index = (intersection.to_f / union.to_f) rescue 0.0
this_book
end.sort_by { |book| 1 - book.jaccard_index }
end
end
# Usage
# Load books from this file
BOOKS = DATA.read.split("\n").map { |l| Book.new(l) }
# Create initial book
this_book = Book.new("Ruby programming language")
# Load recommender
recommender = BookRecommender.new(this_book, BOOKS)
# Find recommendations
recommended_books = recommender.recommendations
# Show books that match the most
recommended_books.each do |book|
puts "#{book.title} (#{'%.2f' % book.jaccard_index})"
end
__END__
Finding the best language for the job
Could Ruby save the day
Python will rock your world
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Python to the moon
Programming languages of the future
@reddyonrails
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K - means is also another option

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