# File lib/gruff/line.rb, line 279
  def normalize(force=false)
    super(force)

    @reference_lines.each_value do |curr_reference_line|

      # We only care about horizontal markers ... for normalization. 
      # Vertical markers won't have a :value, they will have an :index

      curr_reference_line[:norm_value] = ((curr_reference_line[:value].to_f - @minimum_value) / @spread.to_f) if (curr_reference_line.key?(:value))

    end

    #normalize the x data if it is specified
    @data.each_with_index do |data_row, index|
      norm_x_data_points = []
      if data_row[DATA_VALUES_X_INDEX] != nil
        data_row[DATA_VALUES_X_INDEX].each do |x_data_point|
          norm_x_data_points << ((x_data_point.to_f - @minimum_x_value.to_f) /
              (@maximum_x_value.to_f - @minimum_x_value.to_f))
        end
        @norm_data[index] << norm_x_data_points
      end
    end

  end