R - add cran as ubuntu repository and update R

For 11.04

• sudo add-apt-repository "deb http://cran.rakanu.com/bin/linux/ubuntu natty/"
• gpg --keyserver keyserver.ubuntu.com --recv-key E084DAB9
• gpg -a --export E084DAB9 | sudo apt-key add -
• sudo apt-get update
• sudo apt-get upgrade

cran.rakanu.com is my favourite cran mirror, choose one near you (from here)