how to undo set yrange?

[Dave Cottingham]

Here's a simple problem.  Suppose I set yrange, and then later want to
return to the default behavior of automatic range setting.  How do I
undo my set yrange?  yrange (and xrange and zrange) so not appear in
the manual.  I find that the following have no effect:

        set yrange [:]
        set yrange []

Anybody know how to do this?

Thanks,
Dave Cottingham