From 13aed0b2ae57e994e3366fedf15530d86c47bccd Mon Sep 17 00:00:00 2001
From: Brian Underwood <brian@brian-underwood.codes>
Date: Tue, 11 Apr 2017 14:57:32 -0400
Subject: [PATCH] Simplify with #sum

---
 lib/.DS_Store                | Bin 0 -> 6148 bytes
 lib/core_extensions/array.rb |   5 +++--
 lib/decisiontree/id3_tree.rb |   4 ++--
 3 files changed, 5 insertions(+), 4 deletions(-)
 create mode 100644 lib/.DS_Store

diff --git a/lib/.DS_Store b/lib/.DS_Store
new file mode 100644
index 0000000000000000000000000000000000000000..707d6541ef5e81699a5a691e25bfebba6aed5681
GIT binary patch
literal 6148
zcmeHK&5qMB5FU36B-%;@iNhjsu*88&4_%73*Qo5?kU*qj5B!v5W6_|<UM1=FP*n;q
zzyknRe%=Eff+H`%of+Fjtjb<j6`GO8-*`M@C!Zrv3;<$0&-Vc$00>YCJ0Ujz5E>`l
zkdF5d3Oh#)1sKrKK(!Igj%{Rs_O1sxC^*5r`+NTssBBT6W~Iq6=2v!F7IiZi{1Ba;
z?v<<8f-v0eg}v*&7s<>lk|u5D^*F7bQSWiu%(AqaMz@n9S7;p<c{7_ReN?J5r5{xf
z(?+?_i7_Px*tAKSJuTE?8r^(gbdwfZRd#MS$MfSt=VmcBbDh^V-cKF`cjA+umfSE1
zr_tVWc`)4X%X_22sxOzL(V#Ey4-ZzWFt~Mh_~hlAx9{G6`1tAbm#^P!5(xZwt=#aq
zhVN)xNX}VO>C))e7_-h_=P@z^%m6d6<qY^^E7;xg=j6v@2AF}%XMoNJiAorIY#rL8
z0~`8%r135x3EFg*Ae0_skF7%-K@lz$(WMH1#SktX{nE$99$SYl9fVyO=kY5Ge?t*=
zb@WRc4kC8QEi=FjoM&Libt9_(M;G7!&nIz@8DIwfD+WaOFgYCKEBV^G@p4paCF(0w
q5{hdb{z*Z@mST*hQoM(11^to?#Moo&5IrdTBVcLZh8eh227UuVr)CBK

literal 0
HcmV?d00001

diff --git a/lib/core_extensions/array.rb b/lib/core_extensions/array.rb
index c726d5f..3e6e6cb 100644
--- a/lib/core_extensions/array.rb
+++ b/lib/core_extensions/array.rb
@@ -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
diff --git a/lib/decisiontree/id3_tree.rb b/lib/decisiontree/id3_tree.rb
index 9434299..9097ebf 100755
--- a/lib/decisiontree/id3_tree.rb
+++ b/lib/decisiontree/id3_tree.rb
@@ -120,12 +120,12 @@ module DecisionTree
       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]