Gnuplot 如何在四个点之间设置颜色背景？

我想设置4点，并设置它们之间的背景颜色。请问怎么做？如何给x轴上的值的间隔上色？

检查

帮助矩形

，

帮助多边形

和

帮助坐标

代码：

### polygons as background

set object 1 polygon from 0,0 to 1,-0.5 to 5,-1 to 7,0 to 4,1 to 3,0.75
set object 1 fc rgb "green" fs solid 1.0 noborder

set object 2 polygon from -4, graph 1 to graph 0, first 0.4 to -7, screen 0
set object 2 fc rgb "yellow" fs solid 1.0 noborder

set object 3 rectangle from first -3, graph 0 to first 1, graph 1
set object 3 fc rgb "red" fs transparent solid 0.5 noborder

plot cos(x)
### end of code

结果：

### polygons as background

set object 1 polygon from 0,0 to 1,-0.5 to 5,-1 to 7,0 to 4,1 to 3,0.75
set object 1 fc rgb "green" fs solid 1.0 noborder

set object 2 polygon from -4, graph 1 to graph 0, first 0.4 to -7, screen 0
set object 2 fc rgb "yellow" fs solid 1.0 noborder

set object 3 rectangle from first -3, graph 0 to first 1, graph 1
set object 3 fc rgb "red" fs transparent solid 0.5 noborder

plot cos(x)
### end of code

---

检查

帮助矩形

，

帮助多边形

和

帮助坐标

代码：

### polygons as background

set object 1 polygon from 0,0 to 1,-0.5 to 5,-1 to 7,0 to 4,1 to 3,0.75
set object 1 fc rgb "green" fs solid 1.0 noborder

set object 2 polygon from -4, graph 1 to graph 0, first 0.4 to -7, screen 0
set object 2 fc rgb "yellow" fs solid 1.0 noborder

set object 3 rectangle from first -3, graph 0 to first 1, graph 1
set object 3 fc rgb "red" fs transparent solid 0.5 noborder

plot cos(x)
### end of code

结果：

### polygons as background

set object 1 polygon from 0,0 to 1,-0.5 to 5,-1 to 7,0 to 4,1 to 3,0.75
set object 1 fc rgb "green" fs solid 1.0 noborder

set object 2 polygon from -4, graph 1 to graph 0, first 0.4 to -7, screen 0
set object 2 fc rgb "yellow" fs solid 1.0 noborder

set object 3 rectangle from first -3, graph 0 to first 1, graph 1
set object 3 fc rgb "red" fs transparent solid 0.5 noborder

plot cos(x)
### end of code