Coefficient of Variation calculation

lib/descriptive_statistics/coefficient_of_variation.rb

@@ -0,0 +1,11 @@
+module DescriptiveStatistics
+  def coefficient_of_variation(collection = self, &block)
+    values = Support::convert(collection, &block)
+
+    if values.empty?
+      return DescriptiveStatistics.coefficient_of_variation_empty_collection_default_value
+    end
+
+    values.standard_deviation / values.mean
+  end
+end

lib/descriptive_statistics/descriptive_statistics.rb

@@ -4,6 +4,7 @@ def descriptive_statistics(&block)
              :sum => self.sum(&block),
              :variance => self.variance(&block),
              :standard_deviation => self.standard_deviation(&block),
+             :coefficient_of_variation => self.coefficient_of_variation(&block),
              :min => self.min(&block),
              :max => self.max(&block),
              :mean => self.mean(&block),

lib/descriptive_statistics/safe.rb

@@ -6,6 +6,7 @@
 require 'descriptive_statistics/mode.rb'
 require 'descriptive_statistics/variance.rb'
 require 'descriptive_statistics/standard_deviation.rb'
+require 'descriptive_statistics/coefficient_of_variation.rb'
 require 'descriptive_statistics/percentile.rb'
 require 'descriptive_statistics/percentile_rank.rb'
 require 'descriptive_statistics/range.rb'

spec/monkeypatch/array_spec.rb

@@ -37,6 +37,10 @@
       expect(subject.standard_deviation).to eql(2.778310325442932)
     end
 
+    it "calculates the coefficient of variation" do
+      expect(subject.coefficient_of_variation).to eql(0.5659521033309676)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(3.0)
       expect(subject.percentile(50)).to eql(5.0)
@@ -61,4 +65,4 @@
 
    end
 
-end
+end

spec/monkeypatch/empty_collection_spec.rb

@@ -35,6 +35,10 @@
       expect(subject.standard_deviation).to eql(nil)
     end
 
+    it "calculates the coefficient of variation" do
+      expect(subject.coefficient_of_variation).to eql(nil)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(nil)
       expect(subject.percentile(50)).to eql(nil)
@@ -93,6 +97,10 @@
       expect(subject.standard_deviation).to eql(0.0)
     end
 
+    it "calculates the coefficient of variation" do
+      expect(subject.coefficient_of_variation).to eql(0.0)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(0.0)
       expect(subject.percentile(50)).to eql(0.0)
@@ -148,6 +156,10 @@
       expect(subject.standard_deviation).to eql(nil)
     end
 
+    it "calculates the coefficient_of_variation" do
+      expect(subject.coefficient_of_variation).to eql(nil)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(nil)
       expect(subject.percentile(50)).to eql(nil)
@@ -203,6 +215,10 @@
       expect(subject.standard_deviation).to eql(nil)
     end
 
+    it "calculates the coefficient_of_variation" do
+      expect(subject.coefficient_of_variation).to eql(nil)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(nil)
       expect(subject.percentile(50)).to eql(nil)
@@ -227,4 +243,4 @@
 
   end
 
-end
+end

spec/monkeypatch/hash_spec.rb

@@ -37,6 +37,10 @@
       expect(subject.standard_deviation).to eql(2.778310325442932)
     end
 
+    it "calculates the coefficient_of_variation" do
+      expect(subject.coefficient_of_variation).to eql(0.5659521033309676)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(3.0)
       expect(subject.percentile(50)).to eql(5.0)
@@ -61,4 +65,4 @@
 
    end
 
-end
+end

spec/monkeypatch/object_spec.rb

@@ -41,6 +41,10 @@
         expect(subject.standard_deviation(&:price)).to eql(2.0850659461993044)
       end
 
+      it "calculates the coefficient_of_variation" do
+        expect(subject.coefficient_of_variation(&:price)).to eql(0.6043669409273346)
+      end
+
       it "calculates the percentile" do
         expect(subject.percentile(30, &:price)).to eql(2.3)
         expect(subject.percentile(50, &:price)).to eql(3.8)
@@ -116,4 +120,4 @@
     end
    end
 
-end
+end

spec/monkeypatch/set_spec.rb

@@ -37,6 +37,10 @@
       expect(subject.standard_deviation).to eql(2.799416848895061)
     end
 
+    it "calculates the coefficient_of_variation" do
+      expect(subject.coefficient_of_variation).to eql(0.576350527713689)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(2.8)
       expect(subject.percentile(50)).to eql(5.0)
@@ -61,4 +65,4 @@
 
    end
 
-end
+end

spec/monkeypatch/single_value_spec.rb

@@ -31,6 +31,10 @@
       expect(subject.standard_deviation).to eql(0.0)
     end
 
+    it "calculates the coefficient_of_variation" do
+      expect(subject.coefficient_of_variation).to eql(0.0)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(2.0)
       expect(subject.percentile(50)).to eql(2.0)
@@ -55,4 +59,4 @@
 
    end
 
-end
+end

spec/safe/class_method_spec.rb

@@ -32,6 +32,10 @@
       expect(subject.standard_deviation(data)).to eql(2.778310325442932)
     end
 
+    it "calculates the coefficient of variation" do
+      expect(subject.coefficient_of_variation(data)).to eql(0.5659521033309676)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30, data)).to eql(3.0)
       expect(subject.percentile(50, data)).to eql(5.0)
@@ -56,4 +60,4 @@
 
    end
 
-end
+end

spec/safe/extend_spec.rb

@@ -42,6 +42,10 @@
       expect(subject.standard_deviation).to eql(2.778310325442932)
     end
 
+    it "calculates the coefficient of variation" do
+      expect(subject.coefficient_of_variation).to eql (0.5659521033309676)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(3.0)
       expect(subject.percentile(50)).to eql(5.0)
@@ -66,4 +70,4 @@
 
    end
 
-end
+end

spec/safe/stats_spec.rb

@@ -31,6 +31,10 @@
       expect(subject.standard_deviation).to eql(2.778310325442932)
     end
 
+    it "calculates the coefficient of variation" do
+      expect(subject.coefficient_of_variation).to eql (0.5659521033309676)
+    end
+
     it "calculates the percentile" do
       expect(subject.percentile(30)).to eql(3.0)
       expect(subject.percentile(50)).to eql(5.0)
@@ -55,4 +59,4 @@
 
    end
 
-end
+end