How to upgrade to the latest R package in your Ubuntu environment.
Get your latest Ubuntu Linux version by visiting:
https://help.ubuntu.com/community/CheckingYourUbuntuVersion
lsb_release -a and press Enter.
Follow instructions by changing the sources.list files with the correct Ubuntu version. Ensure your mirror is correct in the format of http://cran.stat.sfu.ca/bin/linux/ubuntu
http://askubuntu.com/questions/98749/installing-r-on-ubuntu-getting-updates-to-work
Apply the key as instructed and also upgrade your Ubuntu packages as well.