From paul@stat.auckland.ac.nz  Thu Feb 15 19:19:13 2001
From: paul@stat.auckland.ac.nz (Paul Murrell)
Date: Fri, 16 Feb 2001 08:19:13 +1300
Subject: [Rd] (PR#849)
References: <200102151759.SAA06837@pubhealth.ku.dk>
Message-ID: <007701c09784$2e4e3b10$175dd882@stat.auckland.ac.nz>

Hi


> The symbol( circle) function does not create
> circles.
>
> See following function
>
> ijwbug <- function()
> {
>    plot.new()
>      plot.window(c(-1,1),c(-1,1));
>    symbols(0,0,circle=1,add=T,inches=F);
>
>    curve(sqrt(1 - x^2), from = -1, to = 1, add = T, lty = 1)
>      curve(-sqrt(1 - x^2), from =  -1, to = 1, add = T, lty = 1)
> lines(c(-1,1),c(1,1));
> lines(c(-1,1),c(-1,-1));
>
>
> }


If I understand correctly, I think you're just seeing clipping.

Does the slight modification of your function given below behave as you
would expect ?

ijwbug <- function()
{ 
   # do not clip to figure region, clip only to device region
   par(xpd=NA) 
   plot.new()
   plot.window(c(-1,1),c(-1,1));
   symbols(0,0,circle=1,add=T,inches=F);
   # I have added colour to the curves 
   curve(sqrt(1 - x^2), from = -1, to = 1, add = T, lty = 1, col="red")
   curve(-sqrt(1 - x^2), from =  -1, to = 1, add = T, lty = 1, col="red")
   lines(c(-1,1),c(1,1));
   lines(c(-1,1),c(-1,-1));
}

Paul




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[Rd] (PR#849)
Paul Murrell