R
- Advanced R Programming – Hadley Wickham
- An Introduction to Statistical Learning with Applications in R – Gareth James, Daniela Witten, Trevor Hastie and Robert Tibshirani (PDF)
- Cookbook for R – Winston Chang
- Introduction to Probability and Statistics Using R – G. Jay Kerns (PDF)
- Learning Statistics with R – Daniel Navarro
- Machine Learning with R – Brett Lantz, Packt. (email address requested, not required)
- ModernDive – Chester Ismay and Albert Y. Kim
- Practical Regression and Anova using R – Julian J. Faraway (PDF)
- R for Data Science – Garrett Grolemund and Hadley Wickham
- R for Spatial Analysis (PDF)
- R Language for Programmers – John D. Cook
- R Packages – Hadley Wickham
- R Practicals (PDF)
- R Programming
- R Programming for Data Science – Roger D. Peng (Leanpub account or valid email requested)
- R Succinctly, Syncfusion (PDF, Kindle) (email address requested, not required)
- The caret Package – Max Kuhn
- The R Inferno – Patrick Burns (PDF)
- The R Language
- The R Manuals
- Tidy Text Mining with R – Julia Silge and David Robinson
Racket
Raspberry Pi
- Raspberry Pi Cookbook for Python Programmers – Tim Cox, Packt. (PDF) (email address requested, not required)
- Raspberry Pi: Measure, Record, Explore – Malcolm Maclean (HTML)
- Raspberry Pi Users Guide – (2012) – Eben Upton (PDF)
- The Official Raspberry Pi Project Book (PDF)
REBOL
- Learn REBOL – Nick Antonaccio
Ruby
- A community-driven Ruby style guide
- CodeCademy Ruby
- Developing Games With Ruby – Tomas Varaneckas
- I Love Ruby
- Introduction to Programming with Ruby – Launch School
- Just Enough Ruby to Get By
- Learn Ruby First – Frederick John
- Learn Ruby the Hard Way – Zed Shaw
- Learn to Program – Chris Pine
- Mr. Neighborly’s Humble Little Ruby Book
- Object Oriented Programming with Ruby – Launch School
- Practicing Ruby
- Programming Ruby
- Ruby Essentials
- Ruby Hacking Guide
- Ruby in Twenty Minutes
- Ruby Koans
- Ruby Learning
- Ruby Programming
- Ruby User’s Guide
- Ruby Web Dev: The Other Way – Yevhen Kuzminov
- The Bastards Book of Ruby
- The Unofficial Ruby Usage Guide (at Google) – Ian Macdonald
- Why’s (Poignant) Guide to Ruby
RSpec
Ruby on Rails
- A community-driven Rails style guide
- Building REST APIs with Rails
- Kestrels, Quirky Birds, and Hopeless Egocentricity – Reg Braithwaite
- Learn Ruby on Rails as You Modify a Craigslist Clone
- Objects on Rails
- Rails Girls Guides
- Ruby on Rails 3.2 – Step by Step
- Ruby on Rails 4.0 Guide
- Ruby on Rails Guides
- Ruby on Rails Tutorial (Rails 5): Learn Web Development with Rails – Michael Hartl
- Upgrading to Rails 4