lib/differential/calculator/totals.rb in differential-1.0.2 vs lib/differential/calculator/totals.rb in differential-1.0.3

@@ -14,31 +14,56 @@
     # - b_sigma is the sum of data set B's values.
     # - delta is the difference: b_sigma - a_sigma.
     class Totals
       include ::Differential::Calculator::Side
 
-      attr_reader :a_sigma, :b_sigma
+      attr_reader :a_sigma,
+                  :a_size,
+                  :b_sigma,
+                  :b_size
 
       def initialize
         @a_sigma = 0
+        @a_size  = 0
         @b_sigma = 0
+        @b_size  = 0
       end
 
       def delta
         b_sigma - a_sigma
       end
 
       def add(value, side)
+        increment_sigma(value, side)
+        increment_size(side)
+      end
+
+      private
+
+      def increment_sigma(value, side)
         case side
         when A
           @a_sigma += value
         when B
           @b_sigma += value
         else
           raise ArgumentError, "unknown side: #{side}"
         end
 
-        self
+        nil
+      end
+
+      def increment_size(side)
+        case side
+        when A
+          @a_size += 1.0
+        when B
+          @b_size += 1.0
+        else
+          raise ArgumentError, "unknown side: #{side}"
+        end
+
+        nil
       end
     end
   end
 end