[R] erasing a polygon

[PIKAL Petr]

Hi

It seems that it still works.

x<-c(3,7,7,3)
y<-c(4,4,6,6)
par(bg="pink")
plot(1:10,1:10)
polygon(x, y, border=TRUE, col=0)

> version
               _                                                 
platform       i386-pc-mingw32                                   
arch           i386                                              
os             mingw32                                           
system         i386, mingw32                                     
status         Under development (unstable)                      
major          2                                                 
minor          16.0                                              
year           2012                                              
month          03                                                
day            03                                                
svn rev        58569                                             
language       R                                                 
version.string R Under development (unstable) (2012-03-03 r58569)
>

Regards
Petr

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Terry Therneau
> Sent: Thursday, September 27, 2012 2:37 PM
> To: r-help at r-project.org
> Subject: [R] erasing a polygon
> 
> I'm updating some (very) old code, and one particular option of its
> plot method depends on a once-was-true trick
>      polygon(x, y, border=TRUE, col=0)
>      polygon(x, y, border=TRUE, density=0)
> 
> would draw the polygon AND erase whatever was underneath it back to
> background color.
> 
> Is there a reliable way to do this with the current R (standard
> graphics)?
> 
> Terry Therneau
> 
> PS For the inquiring, the routine is text.rpart with the fancy=T
> option, and the original target was the postscript driver on Splus 3.4.
> (I said it was old.)  The plot.rpart routine draws the branches, and
> text.rpart then wants to lay down some ellipses, erasing what is
> underneath them.
> 
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