I installed R last year for a different class; What do I do now?

Upgrade to latest version.

Simple answer. Download the latest version of R and install it again. With some care, you can quickly update installed packages. Instructions are posted at R packages in Mike’s Biostatistics Book.

The longer answer why you need to reinstall R. The folks at R come up with updates about every month or so. Although your older version of R will continue to work, in this course you will be installing packages to extend R capabilities. If you don’t update, you’ll get error messages when you attempt to load newer packages. Packages are also updated with respect to the latest release of R. So, the conflict for the user comes when you wish to install a package written for a different version of R. At best you’ll get warning messages stating the versions are different; more likely, you won’t be able to install the package at all.