Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:
The following packages have unmet dependencies:
python-rpy2 : Depends: r-base-core (>= 3.1.2) but 3.0.2-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.