swirl

swirl is an interactive R tutorial. Install and load the swirl package.

install.packages('swirl')
library(swirl)

Once the swirl package has loaded you can get started by running

swirl()

There are a few swirl courses. I suggest getting started with R Programming which comes preloaded. You can install other courses

install_course("Exploratory_Data_Analysis")
install_course("Getting_and_Cleaning_Data")
install_course("Data_Analysis")

Once you have installed a course it should show up on the swirl dashboard.