集合知プログラミングのコードをRubyで書く

data.yml

Lisa_Rose:  
  Lady_in_the_Water: 2.5
  Snakes_on_a_Plane : 3.5
  Just_My_Luck: 3.0
  Superman_Returns: 3.5
  You_Me_and_Dupree: 2.5
  The_Night_Litener: 3.0

Gene_Seymour:
  Lady_in_the_Water: 3.0
  Snakes_on_a_Plane : 3.5
  Just_My_Luck: 1.5
  Superman_Returns: 5.0
  You_Me_and_Dupree: 3.5
  The_Night_Litener: 3.0

Michael_Phillips:
  Lady_in_the_Water: 2.5
  Snakes_on_a_Plane : 3.0
  Superman_Returns: 3.5
  The_Night_Litener: 4.0

Claudia_Puig:
  Snakes_on_a_Plane : 3.5
  Just_My_Luck: 3.0
  Superman_Returns: 4.0
  You_Me_and_Dupree: 2.5
  The_Night_Litener: 4.5

Mick_LaSalle:
  Lady_in_the_Water: 3.0
  Snakes_on_a_Plane : 4.0
  Just_My_Luck: 2.0
  Superman_Returns: 3.0
  You_Me_and_Dupree: 2.0
  The_Night_Litener: 3.0
  
Jack_Matthews:
  Lady_in_the_Water: 3.0
  Snakes_on_a_Plane : 4.0
  Superman_Returns: 5.0
  You_Me_and_Dupree: 3.5
  The_Night_Litener: 3.0
  
Toby:
  Snakes_on_a_Plane : 4.5
  You_Me_and_Dupree: 1.0
  Superman_Returns: 4.0
  

recomendations.rb

#!/usr/bin/env ruby
#-*- coding: utf-8 -*-

require "yaml"

data = YAML.load_file "data.yml"

def sim_distance(prefs,person1,person2)
  si = {}
  prefs[person1].each do |item|
    if prefs[person2] != item 
      si[item] = 1
    end
  end
   
  if si.length == 0
    return 0
  end

  sum_of_squares = 0
  prefs[person1].each do |item,point|
    if prefs[person2].has_key?(item)
      s_item = prefs[person1][item] - prefs[person2][item]
      sum_of_squares += s_item ** 2
    end
  end
  1 / (1 + sum_of_squares)
end

puts sim_distance(data, "Lisa_Rose","Gene_Seymour")