how to control which version of a package library() installs?

<snipped>

We should try to explain this, but there is another level of complexity.
If a package has compiled code, unloading the namespace is unlikely to 
unload the DLL (it would need to be done explicitly in .onUnload).
And even then, as I understand it there are OSes on which you cannot 
really unload DLLs, and certainly cannot load another DLL of the same name 
into the process: you get the previously loaded one.

<snipped>

On this, I am quite sure I have managed to crash wine on linux by
dyn.load() an updated version of a DLL of the same name with win32 R in
wine. It is obviously a useful thing to be able to change the source,
re-compile it, and load a new version into R, so that's why I did it,
I think. (and it does work with native R on linux). Genuine windows
may or may not crash, but I don't usually sit in front of windows
for development...

HTL