Add bin and edit workflow

bin/gems/facets-3.1.0/lib/standard/facets/math/variance.rb

@@ -0,0 +1,31 @@
+require 'facets/math/summed_sqdevs'
+
+module Math
+
+  #
+  def self.variance(array, &block)
+    sum2 = if block_given?
+      sum(array){ |i| j = block[i]; j*j }
+    else
+      sum(array){ |i| i**2 }
+    end
+    sum2/array.size - mean(array, &block)**2
+  end
+
+  # Variance of the sample.
+  # Variance of 0 or 1 elements is 0.0.
+  #
+  # TODO: Same as #variance? Then choose one.
+  def self.variance2(array)
+    return 0.0 if array.size < 2
+    summed_sqdevs(array) / (array.size - 1)
+  end
+
+  # Variance of a population.
+  # Variance of 0 or 1 elements is 0.0.
+  def self.pvariance(array)
+    return 0.0 if array.size < 2
+    summed_sqdevs(array) / array.size
+  end
+
+end