[R] par("usr") trouble in multiplot axis scaling

[Johannes Graumann]

Hello,

I'm blotting a series of growth curves into a multiplot environment
created with layout().
since I want the four plots to be easily visually comparable, I do the
following:

#first plot
plot(x,y,<stuff>)
standarduser<-par()$usr
...
<some fitting>
...
lines(spline(x, <fitted_equation>))

#everything all right till here
# second plot
plot(x,y,<stuff>)
par(usr=standarduser)
...
<some fitting>
...
lines(spline(x, <fitted_equation>))

The problem here is, that the axis of the second plot seem to be scaled
according to the parameters of the first, BUT the fitted curve in the
second plot isn't!

Any idea about what I'm doing wrong?

Please help this newbie out of his misery!

Joh