lib/darkext/statistics.rb in darkhelmet-darkext-0.5.2 vs lib/darkext/statistics.rb in darkhelmet-darkext-0.5.3

@@ -64,9 +64,15 @@
 
   def sample_deviation
     self.sample_variance.abs.sqrt
   end
 
+  def geometric_deviation
+    gmean = self.g_mean
+    Math.exp((self.map { |x| (x.ln - gmean.ln).square }.sum.to_f / self.size.to_f).sqrt)
+  end
+  alias :gstddev :geometric_deviation
+
   # Randomly samples n elements
   def sample(n = 1)
     (1..n).collect { self[rand(self.size)] }
   end