R help - Apr 2007 - background color

hi,
  I want to add different colors on the background of a classical plot. Each
color is associated to an interval of the x axis.
  example: the background is red on the interval [1,10], blue on [11,20].
  I try the rect function but it isn't appropriate for the background.
  Can any one can help me please?
  best regards.
     

             
---------------------------------

	[[alternative HTML version deleted]]

What do you mean by background? Maybe this is enough:

plot(seq(-3,3,.01), dnorm(seq(-3,3,.01)), type="n",
xlab="x",
ylab="f(x)", main="Normal density")
polygon(x=c(-4,0,0,-4), y=c(-1,-1,.5,.5), col="red")
polygon(x=c(4,0,0,4), y=c(-1,-1,.5,.5), col="blue")
lines(seq(-3,3,.01), dnorm(seq(-3,3,.01)), type="l", lwd=2)

Play a little bit with the polygon margins to get what you need. You can 
even generate them automatically based on your data.

Petr

yannig goude napsal(a):
> hi,
>   I want to add different colors on the background of a classical plot.
Each color is associated to an interval of the x axis.
>   example: the background is red on the interval [1,10], blue on [11,20].
>   I try the rect function but it isn't appropriate for the background.
>   Can any one can help me please?
>   best regards.
>      
> 
>              
> ---------------------------------
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
-- 
Petr Klasterecky
Dept. of Probability and Statistics
Charles University in Prague
Czech Republic

On 4/17/07, yannig goude <yanniggoude at yahoo.fr>
wrote:
>  I want to add different colors on the background of a classical plot. Each
color is associated to an interval of the x axis.
>  example: the background is red on the interval [1,10], blue on [11,20].
>  I try the rect function but it isn't appropriate for the background..
You can use rect together with par("usr") like this:

usr <- par("usr")
plot(1:20, type = "n")
rect(1, usr[3], 10, usr[4], col = "red")
rect(11, usr[3], 20, usr[4], col = "blue")
points(1:20)

There is also an example of this using polygon in place of rect here:

http://www.mayin.org/ajayshah/KB/R/html/g5.html

and an example of doing it with lattice graphics using xyplot.zoo
(the same idea would work with xyplot) mid way through the examples in:

library(zoo)
?xyplot.zoo