# File lib/prawn/graph/base.rb, line 46
      def initialize(data, document, options = {})
        if options[:at].nil? || options[:at].empty?
          raise Prawn::Errors::NoGraphStartSet,
            "you must specify options[:at] as the coordinates where you" +
            " wish this graph to be drawn from."
        end
        opts = { :theme => Prawn::Chart::Themes.monochrome, :width => 500, :height => 200, :spacing => 20 }.merge(options)
        (@headings, @values, @highest_value) = process_the data
        (grid_x_start, grid_y_start, grid_width, grid_height) = parse_sizing_from opts 
        @colour = (!opts[:use_color].nil? || !opts[:use_colour].nil?)
        @document = document
        @theme = opts[:theme]
        off = 20
        @grid = Prawn::Chart::Grid.new(grid_x_start, grid_y_start, grid_width, grid_height, opts[:spacing], document, @theme)
      end