[R] Problem with par("usr")

[Nicolas STRANSKY]

Hi,

I'm trying to use the "usr" argument but I see no effect of this option 
on my plots. For example:

 > par(usr=c(0,4,0,4))
 > plot(1,1)

This plots one point fine, but the coordinates of the plotting region 
are not those that I specified using par()...
I can check this with
 > par("usr")
[1] 0.568 1.432 0.568 1.432

What can I change in order to have this "usr" argument working ?

The aim of all this is to be able to superpose two plots where xlim and 
ylim arguments are not sufficient for having the same scalings...

Thanks for your help.
-- 
Nicolas STRANSKY
Équipe Oncologie Moléculaire
Institut Curie - UMR 144 - CNRS                 Tel : +33 1 42 34 63 40
26, rue d'Ulm - 75248 Paris Cedex 5 - FRANCE    Fax : +33 1 42 34 63 49