By end-to-end i mean that you can:
(1) read data from SQL or NoSQL DB, excel file, csv, JSON through some REST service, etc.
(2) process it in R
(3) display it to the user through some interactive web interface e.g. using Shiny
It is relatively easy if your app fit the whole loop. I would recommend with some Shiny tutorial to get you started: http://shiny.rstudio.com/tutorial/
But if you need e.g. some stream processing or more complex guis, then R might be not enough I guess.
