0
@@ -2,6 +2,10 @@ This is my attemt to port the code examples from "Programming Collective Intelli
0
 
0
 I try not to stupidly port the stuff, but also try to use ruby idioms and best practices wherevever possible.
0
 
0
+h2. Changelog
0
+
0
+[19.04.2008] - Did some housekeeping. First of all, to make the code as accessible as possible, I converted the python shell stuff into unit tests. I also tried to set up a clever way to load monkey patches such as my Array.sum stuff. YMMV.
0
+
0
 h2. Status
0
 
0
 * Chapter 2

0
@@ -1,50 +1,27 @@
0
-#!/usr/bin/env ruby
0
-require 'yaml'
0
-#
0
-# NOTE: I put the critics data into a yaml file to make it easier to base other language examples on it.
0
-#
0
+require '../lib/examples_helper'
0
+
0
+# TODO: This probably belongs into a module
0
 
0
-#
0
-# INFO: Both the code and the result of the original python version from the book are
0
-# broken, so don't expect the sim_distance function to return the result stated in the book.
0
-#
0
 def sim_distance(prefs, person1, person2)
0
-  si = []
0
-  prefs[person1].each do |k,v|
0
-    if prefs[person2].has_key?(k)
0
-      si << k
0
-    end
0
-  end
0
-  
0
+  si = prefs[person1].keys & prefs[person2].keys
0
   return 0 if si.size == 0
0
   
0
   sum_of_squares = si.inject(0) do |sum, item|
0
     sum + ((prefs[person1][item] - prefs[person2][item]) ** 2)
0
   end
0
-  puts sum_of_squares
0
   1/(1 + Math.sqrt(sum_of_squares))  
0
 end
0
 
0
 def sim_pearson(prefs, person1, person2)
0
-  si = []
0
-  prefs[person1].each do |k,v|
0
-    if prefs[person2].has_key?(k)
0
-      si << k
0
-    end
0
-  end  
0
+  si = prefs[person1].keys & prefs[person2].keys
0
   return 0 if si.size == 0
0
-
0
-  sum1 = si.inject(0) { |sum, k| sum + prefs[person1][k] }
0
-  sum2 = si.inject(0) { |sum, k| sum + prefs[person2][k] }
0
-  sum1_sq = si.inject(0) { |sum, k| sum + (prefs[person1][k] ** 2) }
0
-  sum2_sq = si.inject(0) { |sum, k| sum + (prefs[person2][k] ** 2) }
0
-
0
-  p_sum = si.inject(0) { |sum, k| sum + (prefs[person1][k] * prefs[person2][k])}
0
-
0
+  sum1 = si.sum {|k| prefs[person1][k] }
0
+  sum2 = si.sum {|k| prefs[person2][k] }
0
+  sum1_sq = si.sum {|k| prefs[person1][k] ** 2 }
0
+  sum2_sq = si.sum {|k| prefs[person2][k] ** 2 }
0
+  p_sum = si.sum { |k| (prefs[person1][k] * prefs[person2][k])}
0
   num = p_sum - (sum1 * sum2 / si.size)
0
   den = Math.sqrt((sum1_sq - (sum1 ** 2) / si.size) * (sum2_sq-(sum2 ** 2)/ si.size))
0
   return 0 if den == 0
0
   num/den
0
-end
0
-
0
-@critics = YAML.load_file('recommendations.yml')
0
+end
0
\ No newline at end of file