[R] Upgrade process for libraries: can I use installed.packages on an old installation followed by install.packages in a new one

[Erik Iverson]

Ted Byers wrote:
> I tend to have a lot of packages installed, in part because of a wide
> diversity of interests and a disposition of examining different ways to
> accomplish a given task.
> 
> I am looking for a better way to upgrade all my packages when I upgrade the
> version of R that I am running.
> 
> On looking at support for installing and updating packages, I found these
> two: installed.packages() and  install.packages() and it occurred to me that
> in principle I ought to be able to use the one in the original installation
> to get a list of packages I'm working with and and put its output into a
> plain text file that I can read in the new installation and pass to the
> other to ensure the new installation has a fresh installation of all the
> packages I want to work with.

I must be missing the obvious, but what's wrong with update.packages() ?