R packages for Cosmic Cuttlefish (18.10) have been added to the RRutter3.5 PPA and therefore have been mirrored to CRAN. These are the base packages for R, plus the recommended packages as well as a couple of others (jags, ess, rpy2, and littler). Most of these are already available in the standard 18.10 repositories, but as packages are updated, I will update them for CRAN.
Since the lifespan of Cosmic Cuttlefish is so short (support ends July 2019), I will not be creating a version of c2d4u for Cosmic. If you want access to all of those packages, I suggest sticking to an LTS. And with Ubuntu’s announcement that support for Bionic (18.04) has been extended to 10 years, it will be around for a while.