[R] Pointing to a specific place on the x-axis with an arrow

[Barry Rowlingson]

On Wed, Oct 6, 2010 at 12:29 PM, Ivan Calandra
<ivan.calandra at uni-hamburg.de> wrote:
>  Hi again,
>
> Just one little question. I don't understand what "clipping" is.
> Probably a problem with English...
> Therefore the par(xpd=NA) is not really clear for me; nor is the clip()
> function. And I don't see any difference between par(xpd=NA) and nothing.
>
> It's not really related to this post, let me know if I should change the
> subject.

Try this:

 > par(xpd=FALSE)
 > plot(1:10)
 > abline(h=4)
 > par(xpd=NA)
 > abline(h=5)

 the first horizontal line, at y=4, should only be visible in the box
of the plot. The second line, at y=5, should go right across the
graphics window. We say the first line is 'clipped' to the box.

 so, to draw some things outside the box you have to set par(xpd=NA)
first. Its not necessary with things like mtext and axis because they
obviously are going to draw outside the box anyway. It's just for
points, lines, symbols, arrows etc.

Barry