An introduction to R, CRAN project
Everything you need to know to get you started.
RStudio Cheat Sheets, RStudio
Cheat Sheets of using R for various purposes from the Base R all the way to deep learning with R.
Quick-R
A quick access to R, especially if you are from Stata, SAS, SPSS etc.
R for Data Science, Garrett Grolemund and Hadley Wickham
Don’t miss the exercises.
Advanced R, Hadley Wickham
R programming.
Data Science Specialization, John Hopkins University
R programming + data analysis + research workflow.
Statistics with R Specialization, Duke University
Some people find the JHU course too R heavy. This specialization focuses on teaching statistics where people learn to use R through projects.