Add bin and edit workflow

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

@@ -0,0 +1,27 @@
+require 'facets/math/variance'
+
+module Math
+
+  # Standard deviation of a sample.
+  #
+  def self.std(array, &block)
+    sqrt(variance(array, &block))
+  end
+
+  class << self
+    alias_method :standard_deviation, :std
+  end
+
+  # Standard deviation of a population.
+  #
+  def self.pstd(array, &block)
+    Math::sqrt(pvariance(array, &block))
+  end
+
+  # Calculates the standard error of a sample.
+  def self.stderr(array)
+    return 0.0 if array.size < 2
+    std(array) / sqrt(array.size)
+  end
+
+end