sudo emerge --sync

RStudio requires several packages to be installed first. You can do this by running:

   sudo emerge -av dev-lang/r dev-ruby/gems dev-python/pip

Gentoo uses Portage for package management, but you might need to add a custom repository if it's not already available. You can do this by adding the following line to `/etc/portage/repos.conf/`:

   [rstanford]
   location = /var/lib/portage/rstanford
   sync-type = git
   sync-uri = https://github.com/gentoo-rscience/packages.git
   auto-sync = yes

Once the repository is added, you can install RStudio by running:

   sudo emerge -av app-editors/rstudio

After installation, you can start RStudio from your terminal or through your application menu.

If you encounter any issues during the installation process, make sure to check the Gentoo forums or the RStudio community for additional support.