- R reference card
- Quick Graphics and Graphics and Murrel's Graphics
- Quick R
- R-Spatial and Spatial R
- California Soil Resources Lab
- Videos and video tutorials and the Google R Videos
- Search engines
- R Site search
- The Guerilla guide to R
- R Inferno give a stimulating alternative vision of R.
- Here you can download the Matlofs book, The Art of R Programming.
- And here you can download a book on ggplot2 by its own author Hadley Wickham, and other ggplot resources.
- Three-Toed Sloth's book is a fresh-air statistical book which uses R.
- Here you will find the book on "Modeling data with functional programming in R" by Bryan Lee Yung Row
- A curated list of awesome packages and R-related stuff
- Last, but not least, Hadley Wickham book' and Advanced R.
If you have further questions, ask Stackoverflow
If you managed to learn how to write function, please decide to make a package. Emanuele Cordano found this nice post on github explaining why to do (thinking to statistics).
An alternative pathway of instructions is here.