Defining range of x and y axis in pairs()

Hi,

I have a problem to define the range of x and y axis in pairs() for my
scatterplots. In low-level plots I can specify that by providing xlim
and ylim. This also works for pairs() even if warnings tell me that it
doesn't (see below).

But if I add upper.panel and/or lower.panel it doesn't work - I get an
error message saying that there's an error in "upper.panel
(as.vector(x[, j]), as.vector(x[, i]), ...)"!?

I know that (according to ?pairs) graphical parameters can be passed to
pairs() and xlim/ylim are *not* graphical parameters - I just wonder
why it anyway works in the first case.

Can anyway tell me how to adjust my pairs statement either using
xlim/ylim in a different way or by using totally different options?
(I'm a newbie to R)


# This works!
pairs(x, panel=points, xlim=c(-2,2));

# This one doesn't work
pairs(x, panel=points, xlim=c(-2,2), lower.panel=panel.cor,
upper.panel=panel.smooth);

# this is the function for lower.panel
   panel.cor <- function(x, y)
   {
       usr <- par("usr"); on.exit(par(usr))
       par(usr = c(0, 1, 0, 1))
       txt <- cov(x, y, use="pairwise.complete.obs");
       text(0.5, 0.5, txt);}
  }

Thanks!