#!/usr/bin/ruby
require 'descriptive_statistics'
class MyList < Struct.new(:id, :name,:friends)
end
arr = Array.new
f = File.open("test-comma.txt", "r")
f.each_line { |line| words = line.split(',')
   p = MyList.new
   p.id=words[0]
   p.name=words[1]
   p.friends=words[2]
   arr.push(p)
   }
f.close

arr.collect{|p| p.friends}.standard_deviation