After a bit of initial hesitation (will I lose my packages during the new installation? etc.) I finally took some courage and decided to follow the official documentation on CRAN.
(A library is a directory where packages are stored.) One problem is that, after upgrading to a new version of R, packages are no longer found because there is a new library.This strategy helps you identify packages that have been installed in your old version of R so you can then reinstall the into your new version of R.You can install packages into your new version of R by choosing, from the pulldown menu, Packages and then Install Packages from CRAN.That is OK because you can use the update.packages() function to bring your packages up to date, like this. It is not easy to figure out how to update the core R package, but, like most things in linux, it comes down to a correctly ordered set of calls to a package manager.The article of this document is to explain these problems, and how to fix them.