def draw_line_markers
return if @hide_line_markers
@radius = @graph_height / 2.0
@center_x = @graph_left + (@graph_width / 2.0)
@center_y = @graph_top + (@graph_height / 2.0) - 10
@d = @d.stroke(@marker_color)
@d = @d.stroke_width 1
(0..@column_count-1).each do |index|
rad_pos = index * Math::PI * 2 / @column_count
@d = @d.line(@center_x, @center_y, @center_x + Math::sin(rad_pos) * @radius, @center_y - Math::cos(rad_pos) * @radius)
marker_label = labels[index] ? labels[index].to_s : '000'
draw_label(@center_x, @center_y, rad_pos * 360 / (2 * Math::PI), @radius, marker_label)
end
end