Use Emacs Speaks Statistics.

Also install company-mode for tag completion.

Write your code in an R buffer, attach it to an R session, then use eval commands to run R code from your buffer in the session.

You can use M-x ess-remote to run an R session on another computer.

ess-build-tags-for-directory lets you make a lookup table for your code. Then you can use M-. to jump to definitions.