line plot在circos中的用法比较简单，示例如下：
对于折线图而言，调整外观的属性有以下4个
1. thickness
thickness 控制线条的粗细
2. color
color 控制线条的颜色
3. fill_color
fill_color控制填充色，在折线的下方进行颜色填充
4. max_gap
在直线图中，会看到如下所示的分割线，max_gap的作用就是设置分割线的间距，max_gap = 1u 代表每隔1个单位画一条分割线，其用法和ticks类似
控制位置的属性在前面的文章中我们已经介绍过了，这里在重复一遍。
r0和r1分别设置圆环的内径和外径，max和min设置y轴的最大值和最小值，orientation控制y轴0点的位置，orientation = in代表 y = 0 位于r1上；orientation = out表示y = 0位于r0 上；z代表优先级，数值越大，优先级越高，当两个折线图重叠时，优先级高的会有优先显示。
与backgrounds, axes, rules的结合使用，在scatter plot中，我们也介绍过了，今天解锁一种axes的新用法，代码如下
在之前的文章中，我们看到了用y0, y1指定范围，在用spacing参数设定间隔的用法, 这种用法方便的设置多条轴线，今天的这个例子中，通过position直接设置轴线的位置，用于指定单条轴线。
最后放一张line plot的示例，在下图中，除去染色体外，包括3个line plot; 最内圈的line plot有3种填充色，背景色也有3种，另外两圈的line plot中，其axes的定义就是使用了position的用法，可以看到其轴线非常少，只有2,3条；最内圈的line plot的轴线则采用spacing的用法，其轴线非常多，而且均匀分布
完整代码如下
<<include colors_fonts_patterns.conf>>
<<include ideogram.conf>>
<<include ticks.conf>>
<image>
<<include etc/image.conf>>
</image>
karyotype = data/karyotype/karyotype.human.txt
chromosomes_units = 1000000
chromosomes = hs1 # ;hs2;hs3
chromosomes_display_default = no
<plots>
type = line
thickness = 2
<plot>
max_gap = 1u
file = data/6/snp.density.250kb.txt
color = vdgrey
min = 0
max = 0.015
r0 = 0.5r
r1 = 0.8r
fill_color = vdgrey_a3
<backgrounds>
<background>
color = vvlgreen
y0 = 0.006
</background>
<background>
color = vvlred
y1 = 0.002
</background>
</backgrounds>
<axes>
<axis>
color = lgrey_a2
thickness = 1
spacing = 0.025r
</axis>
</axes>
<rules>
<rule>
condition = var(value) > 0.006
color = dgreen
fill_color = dgreen_a1
</rule>
<rule>
condition = var(value) < 0.002
color = dred
fill_color = dred_a1
</rule>
</rules>
</plot>
# outside the circle, oriented out
<plot>
max_gap = 1u
file = data/6/snp.density.txt
color = black
min = 0
max = 0.015
r0 = 1.075r
r1 = 1.15r
thickness = 1
fill_color = black_a4
<axes>
<axis>
color = lgreen
thickness = 2
position = 0.006
</axis>
<axis>
color = lred
thickness = 2
position = 0.002
</axis>
</axes>
</plot>
<plot>
z = 5
max_gap = 1u
file = data/6/snp.density.1mb.txt
color = red
fill_color = red_a4
min = 0
max = 0.015
r0 = 1.075r
r1 = 1.15r
</plot>
# same plot, but inside the circle, oriented in
<plot>
max_gap = 1u
file = data/6/snp.density.txt
color = black
fill_color = black_a4
min = 0
max = 0.015
r0 = 0.85r
r1 = 0.95r
thickness = 1
orientation = in
<axes>
<axis>
color = lgreen
thickness = 2
position = 0.01
</axis>
<axis>
color = vlgreen
thickness = 2
position = 0.008
</axis>
</axes>
<axis>
color = vlgreen
thickness = 2
position = 0.006
</axis>
<axis>
color = red
thickness = 2
position = 0.002
</axis>
</axes>
</plot>
<plot>
z = 5
max_gap = 1u
file = data/6/snp.density.1mb.txt
color = red
fill_color = red_a4
min = 0
max = 0.015
r0 = 0.85r
r1 = 0.95r
orientation = in
</plot>
</plots>
<<include etc/housekeeping.conf>>