RES: How to force axis to have the same range

Thanks to all the people who answer my question. It is know clear to know
how to produce a square shape graph... but I guess there is no easy way to
force the x and the y axis to have the same limits.

If you mean the general case where you don't want to specify xlim and
ylim explicitly, then in lattice you can use

xyplot(...
       prepanel = function(x, y, ...) {
           rng <- range(x, y, finite = TRUE)
           list(xlim = rng, ylim = rng)
       })

-Deepayan