Simplify with #sum

Author: cheerfulstoic

lib/.DS_Store

@@ -2,9 +2,10 @@ class Array
   def entropy
     each_with_object(Hash.new(0)) do |i, result|
       result[i] += 1
-    end.values.inject(0) do |sum, count|
+    end.values.sum do |count|
       percentage = count.to_f / length
-      sum + -percentage * Math.log2(percentage)
+
+      -percentage * Math.log2(percentage)
     end
   end
 end

lib/core_extensions/array.rb

@@ -120,12 +120,12 @@ def id3_discrete(data, attributes, attribute)
       index = attributes.index(attribute)
 
       values = data.map { |row| row[index] }.uniq
-      remainder = values.sort.inject(0) do |sum, val|
+      remainder = values.sort.sum do |val|
         classification = data.each_with_object([]) do |row, result|
           result << row.last if row[index] == val
         end
 
-        sum + ((classification.size.to_f / data.size) * classification.entropy)
+        ((classification.size.to_f / data.size) * classification.entropy)
       end
 
       [data.classification.entropy - remainder, index]