[R-pkg-devel] Advice on dealing with absent dependencies

[J C Nash]

Although I have been working with R for quite a while, I still find some issues
of dependencies troubling. In particular, my optimr package is set up to allow
users to access many function minimization tools via a single wrapper. In the past
I've had notices from CRAN to fix things when called packages fail. To avoid such
messages, the CRAN version has a limited set of solvers, and I've put the full
version (optimrx) on R-forge.

I'm now thinking I should try to adjust optimr so that it works with all the solvers
it has available (a user may not want to install them all, for example), and does
not give more than a warning when one or more is unavailable.

Can someone point me to best practise for doing this sort of conditional operation?
While I've some ideas, I'd prefer to do things right and not give the CRAN
admins any extra work. Assuming I succeed, I'll happily prepare a write-up if one
is not available.

Cheers,

John Nash