R is a free software package for statistical computing. It is part of most Linux distributions. However the latest version of R is not always available. To install the latest version of R we need to add the URL of a CRAN mirror to a file in /etc/apt/sources.list.d.
CRAN is a network of ftp and web servers that provide upto date information on R such as documentation, source code and news about R development. To install R, we need to issue the commands:
apt-get install r-base r-base-dev
To update R to a newer version we need to replace the CRAN URL in /etc/apt/sources.list.d, with a URL that points to the newer version of R. After that we need to issue the commands:
Since the new CRAN URL requires different package signing keys, we will get an error similar to: “following signatures couldn’t be verified because the public key is not available: NO_PUBKEY”.
The solution is to import the package signing keys for the new R package using the command:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys [key_name]
where key_name is the short signature of the missing key as indicated in the error message. After that the apt-get upgrade command should work without problems.
See the R official documentation for more information.