# [Rd] (PR#849)

Peter Dalgaard BSA p.dalgaard@pubhealth.ku.dk
15 Feb 2001 22:22:01 +0100

"Paul Murrell" <paul@stat.auckland.ac.nz> writes:

> Hi
>
>
> > The symbol( circle) function does not create
> > circles.
> >
> > See following function
> >
> > ijwbug <- function()
> > {
> >    plot.new()
> >      plot.window(c(-1,1),c(-1,1));
> >
> >    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));
>    # 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

Actually, I think the real problem is that the plotting region is not
square, so  curve(sqrt(1 - x^2),...) is an ellipse. Insert
par(pty="s") to fix that.

--
O__  ---- Peter Dalgaard             Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
(*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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