According to the info provided in the survey link in Mauricio's answer, you can use RGedit with Pluma editor, which is available from the repos:
sudo apt install pluma
Pluma is a fork of gedit2, maintained by Mate desktop project.
Alternatively, I personally felt in love with Sublime Text + sublimeREPL plugin combo, which works splendidly for me. Sublime Text is light and fast and at the same time very advanced editor (and my most favourite piece of software, because it's such a problem solver) and I highly recommend it to anyone who's looking for good editor. The R implementation is almost on par with Rstudio, however it's much lighter on resources. There are keyboard shortcuts for sending code from script to R session, you can make plots (making screenshots of just focused window saves plots without window decorations, at least in elementaryOS on my small netbook, where I use this setup), navigate console history on a minimap (including printed help). As a bonus (compared to gedit), Sublime Text has the best and most flexible implementation of multiple cursors I've seen so far (e.g. Rstudio has it, but rather cumbersome to use practically), which is a huge helper every day.
emacs
withess
and it works like a charm, you might want to give it a spin too :) – jena Jul 27 '16 at 07:21