TICKS AT SPECIFIC POSITIONS

之前的操作都是对整个环均匀地加上标签，这一节我们将介绍如何给特定位置添加标签。 具体的方法是运用position / rposition

绝对位置：

<ticks>

...

<tick>
# define position 
position     = 25u
# no spacing definition necessary
...
</tick>

<tick>
# define multiple positions
position     = 30u,32u,34u,40u
...
</tick>

...

</ticks>

相对位置

<tick>
# define multiple positions
rposition      = 0.5,0.7,0.9
spacing_type   = relative
color          = blue
label_relative = yes
format         = %.2f
</tick>

起始终止

还可以特殊地加上3'和5'的标记

<tick>
position = start
label    = 3'
...
</tick>

<tick>
position = end
label    = 5'
...
</tick>