Installing R from CRAN Ubuntu repository: No Public Key Error

Question

I am on R version 2.13 and would like to update to a newer version in order to use some packages that depend on R>= 2.14.

I have the line to my sources.list file as

Answer 1

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys KEYID

and replace KEYID with the number shown in the error message.