Grid

有的时候我们会看到这样的图：

我们可以随意地延伸刻度。注意这种延伸会覆盖在highlights上，但是在其他所有数据类型下面 半径当然也是我们可以控制的。

show_grid  = yes

<ticks>

 grid_start     = 0.5r
 grid_end       = 0.975r
 grid_color     = black
 grid_thickness = 2p
 ...
 <tick>
  spacing = 1u
  ...
  grid           = yes
  grid_color     = grey
  grid_thickness = 1
  grid_start     = 0.55r
  grid_end       = 0.95r
 </tick>
 <tick>
  spacing = 5u
  ...
  grid           = yes
  grid_color     = dgrey
  grid_thickness = 2
  grid_start     = 0.6r
  grid_end       = 0.925r
 </tick>
 <tick>
  spacing = 10u
  ...
  grid           = yes
  grid_color     = black
  grid_thickness = 2
 </tick>
</ticks>