# File temp/Graph/Plot.rb, line 137
      def add_data data
        @data = [] unless @data

        raise "No data provided by #{conf.inspect}" unless data[:data] and
        data[:data].kind_of? Array
        raise "Data supplied must be x,y pairs!  "+
          "The data provided contained an odd set of "+
          "data points" unless data[:data].length % 2 == 0
        return if data[:data].length == 0

        x = []
        y = []
        data[:data].each_index {|i|
          (i%2 == 0 ? x : y) << data[:data][i]
        }
        sort( x, y )
        data[:data] = [x,y]
        @data << data
      end