0
@@ -9,4 +9,15 @@ class Array
0
     end
0
   end
0
   
0
+  def mean
0
+    return GSL::Stats.mean1(self)
0
+  end
0
+  
0
+  def variance
0
+    return GSL::Stats.variance1(self)
0
+  end
0
+  
0
+  def sd
0
+    return GSL::Stats::sd1(self)
0
+  end
0
 end
0
\ No newline at end of file

0
@@ -7,5 +7,27 @@ describe Array do
0
     it "should return a real number" do
0
       [1, 2, 3].correlation([1, 2, 3]).should be_close(1.0, 0.001)
0
     end
0
+    
0
+    it "should raise an ArgumentError if the two arrays are of different sizes" do
0
+      lambda { [1, 2, 3].correlation([1, 2]) }.should raise_error(ArgumentError)
0
+    end
0
+  end
0
+  
0
+  describe "calculating the mean" do
0
+    it "should return a real number" do
0
+      [1, 2, 3].mean.should be_close(2.0, 0.0001)
0
+    end
0
+  end
0
+  
0
+  describe "calculating the variance" do
0
+    it "should return a real number" do
0
+      [1, 2, 3].variance.should be_close(1.0, 0.0001)
0
+    end
0
+  end
0
+  
0
+  describe "calculating the standard deviation" do
0
+    it "should return a real number" do
0
+      [2, 2, 2].sd.should be_close(0.0, 0.0001)
0
+    end
0
   end
0
 end
0
\ No newline at end of file