“Cantor is an application that lets you use your favorite mathematical applications from within a nice KDE-integrated worksheet interface. It offers assistant dialogs for common tasks and allows sharing of worksheets with others. Available backends are Sage, Maxima, R, and KAlgebra.”
Sadly R backend is not supported in kubuntu (see here) because r-base package is in universe and therefore kde-edu package cannot depend on it.
Anyway, if you need R support, you probably already enabled universe repository, and you can find on my PPA with R backend.
To install it just add my PPA to your software sources (you also need kubuntu-ppa/backports repository enabled) and upgrade
sudo add-apt-repository ppa:daniele.domenichelli/ppa
sudo apt-get update
sudo apt-get upgrade
