When installing packages, the message There are binary versions available but the source versions are later often appears. This is (I think) followed by the question Do you want to install from sources the package which needs compilation?.
What does the message mean? And what response (y or n) is recommended and in what situations?
This often means that the package has updated recently on CRAN but the binary isn't yet available for your OS (can take a day or two). There are probably other scenarios when the binary isn't available for your platform.
If you say no, you won't get the most recent version. But this might be just fine, unless you were specifically installing because of an update.
If you say yes, the package will be built from source locally. If it has compiled code and you've never set up build tools for R, then this won't actually succeed.
Is there an option in install.packes() in order to say yes and avoid the necessity for the user to type something interactively?
Hi @jennybryan,
Thanks for your reply, it helped me too, a lot. I'd like to do just that, install locally from tar.gz (is it even possible to install a package whose binary is not yet available for Windows?) but I don't know how to set up the build tools for R. Could you point me in the right direction?
Thank you!
PS: you must have guessed my level of newbieness , so please forgive my unintentional stupidity.
Jumping in (and quoting myself, to boot! 
), but in case it's helpful, here's a bit of related discussion from another thread:
Hi @jcblum,
Thank you! Your answer is exactly what I needed.
Now, after reading it, I'm a bit ashamed I didn't peruse the forum for it...
you've just stepped up there with my r-angels.