shading area between two lines in r

Question

For example if i need to shade two area in plot

x<-rep(1:10)
plot(x,type="h")

I need as an example shade the area from 1 to 3 and from 7 to 10,

I use this commands but it omitted the lines of plot.

usr <- par('usr')
rect(1, usr[3], 3, usr[4], col='green')

Answer 1

If I understand you correctly, you can get what you want by using the little-known panel.first= argument to plot.default():

plot(x,type="h", 
     panel.first = {
         usr <- par('usr')
         rect(c(1,7), usr[3], c(3,10), usr[4], col='green', border=NA)
     })

Or, to avoid any mucking around with par('usr') values, just do:

plot(x, type="h", 
     panel.first = rect(c(1,7), -1e6, c(3,10), 1e6, col='green', border=NA))

Answer 2

See ?polygon:

polygon( x = c(1,1,3,3,1), y=c( usr[1], x[1], x[3], usr[1], usr[1]) ,col="red")

> polygon( x = c(1,1,3,3,1), y=c( usr[1], x[1], x[3], usr[1], usr[1]) ,col="red")
> polygon( x = c(7,7,10,10,7), y=c( usr[2], x[7], x[10], usr[1], usr[1]) ,col="red")

I chose to close the polygon but seem I remember you can get it to self-close.