Make installed packages available to new R version

After installing a new version of R, how do I make the packages that I 
have already installed and use on the old version available to the new 
version?

Here is my solution. It has worked over many releases of R,
though it will probably require one initial re-installation of
packages.

Set environment variable R_LIBS to some permanent directory
before installing a version of R. (That is, NOT a directory
under the tree of your current R version.) When you subsequently
install packages, they will go into that location and won't need
re-installation with each new version of R. 

It's still necessary to run update.packages() periodically --
such as after installing a new R version -- to keep the
installed packages current.

Mike Prager, NOAA, Beaufort, NC
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