Four arithmetic operations

lib/nyaplot/data.rb

@@ -223,6 +223,16 @@ def label
       @label
     end
 
+		[:+, :-, :/, :*].each do |operator|
+			define_method(operator) do |obj|
+				if obj.is_a? Nyaplot::Series
+					Nyaplot::Series.new(label, (self.zip obj.to_a).map { |arr| arr.inject(&operator) })
+				elsif obj.is_a? Numeric
+					Nyaplot::Series.new(label, self.map { |e| e.send(operator, obj) })
+				end
+			end
+		end
+
     def method_missing(meth, *args, &block)
       if @arr.respond_to?(meth)
         @arr.send(meth, *args, &block)

spec/nyaplot/data_spec.rb

@@ -176,4 +176,60 @@
       expect(@series.size).to eq(@series.to_a.size)
     end
   end
+
+  context "#+" do
+    it "should add each element of the two Series" do
+      another_series = Nyaplot::Series.new('another_series', [20, 40])
+
+      expect((@series + another_series).to_a).to eq( [30, 70] )
+    end
+
+    it "should add the number to each element of the Series" do
+      number = 10
+
+      expect((@series + number).to_a).to eq( [20, 40] )
+    end
+  end
+
+  context "#-" do
+    it "should subtract the passed Series from the Series" do
+      another_series = Nyaplot::Series.new('another_series', [20, 40])
+
+      expect((@series - another_series).to_a).to eq( [-10, -10] )
+    end
+
+    it "should subtract the number from the Series" do
+      number = 10
+
+      expect((@series - number).to_a).to eq( [0, 20] )
+    end
+  end
+
+  context "#/" do
+    it "should divide each element of the Series by the each element of the passed Series" do
+      another_series = Nyaplot::Series.new('another_series', [20.to_f, 40.to_f])
+
+      expect((@series / another_series).to_a).to eq( [10/20.to_f, 30/40.to_f] )
+    end
+
+    it "should divide each element of the Series by the passed number" do
+      number = 10.to_f
+
+      expect((@series / number).to_a).to eq( [10/10.to_f, 30/10.to_f] )
+    end
+  end
+
+  context "#*" do
+    it "should multiply each element of the two Series together" do
+      another_series = Nyaplot::Series.new('another_series', [20, 40])
+
+      expect((@series * another_series).to_a).to eq( [200, 1200] )
+    end
+
+    it "should multiply each element of the Series by the number" do
+      number = 10
+
+      expect((@series * number).to_a).to eq( [100, 300] )
+    end
+  end
 end