[R] Is abline misbehaving?

[Jim Lemon]

Hi experts,
I was graciously offered a function to enhance abline by restricting the 
extent of the line to less than the plotting region. This seems a useful 
idea, and it looked like the easiest way to program it was to set up a 
clipping region with "clip", draw the abline and then restore the 
previous clipping region. Let us call this function ablineclip. After 
quite a bit of testing, I have found that the first call to ablineclip 
ignores the clipping region. It's not that simple. Successive calls to 
ablineclip respect the clipping region, even if it changes. I can 
reproduce the behavior like this:

plot(-3:3,-3:3)
clip(-2,2,-2,2)
abline(v=0)
clip(-2,2,-2,2)
abline(h=0)


The first abline ignores the clip, the second respects it. I have 
programmed around this, with the pathetic kludge of calling "abline" 
with a line outside the plotting area, calling "clip" a second time, and 
then calling "abline" with the line that was requested. While this 
works, my place in programming history will be ineradicably compromised 
if the Programmers' Hall of Fame ever finds out. Any suggestions?

R-2.7.2
FC9 Linux

Jim