Is it possible to get code completion for R in Emacs ESS similar to what is available in Rstudio?

Question

Rstudio has a great code completion feature. It provides a quick view of functions that start with a given string, as well as function and parameter definitions.

ESS

Answer 1

[EDIT: This is an old answer and auto-complete package dropped out of fashion since then. Please use company-mode instead. It should work by default. Wiki configuration entry is here.]

Recent versions of ESS (> v.12.02) integrate with auto-complete package out of the box (you need not configure anything, just install auto-complete). It provides help on arguments as well as function help. I added detailed instructions to the wiki

Ess-eldoc was also rewritten and from v.12.02 it's active by default, so you don't need to configure anything.