Simple client side function for determining outliers in a set

outliers.rb

module MCollective
  class Aggregate
    class Outliers<Base

      def startup_hook
        result[:value] = {:high => [], :low =>[]}
        result[:type] = :collection
        @aggregate_format = "%s : %s" unless @aggregate_format

        @data_set = []
        @quartiles = {:high => nil,
                      :low=> nil}
      end 

      def process_result(value, reply)
        @data_set << value
      end 

      def summarize
        @data_set.sort!
        set_quartiles
        find_outliers
      end 

      def set_quartiles
        n = @data_set.size
        l = Float((1.0/4.0)*(n + 1)) 
        u = Float((3.0/4.0)*(n + 1)) 

        l = l.truncate + 1 unless Integer(l) == l
        u = u.truncate

        iqr = @data_set[u] = @data_set[l]
        @quartiles[:low] = @data_set[l] - (1.5 * iqr)
        @quartiles[:high] = @data_set[u] + (1.5 * iqr)
      end 

      def find_outliers
        @data_set.each do |data_item|
          result[:value][:high] << data_item if data_item > @quartiles[:high]
          result[:value][:low] << data_item if data_item < @quartiles[:low]
        end 
      end 
    end 
  end 
end