y_range (SVG::Graph::Plot)

    # File temp/Graph/Plot.rb, line 214
          def y_range
            max_value = @data.collect{|x| x[:data][Y].max }.max
            min_value = @data.collect{|x| x[:data][Y].min }.min
            min_value = min_value<min_y_value ? min_value : min_y_value if min_y_value

            range = max_value - min_value
            top_pad = range == 0 ? 10 : range / 20.0
            scale_range = (max_value + top_pad) - min_value

            scale_division = scale_y_divisions || (scale_range / 10.0)

            if scale_y_integers
              scale_division = scale_division < 1 ? 1 : scale_division.round
            end

            return [min_value, max_value, scale_division]
          end