This part of portfolio doesn't pretend to be the ultimate library of the whole universe of resources available out there...
R Coding
Hands-On Programming with R by Garrett Grolemund
R for Data Science (1st edition) by Garrett Grolemund, Hadley Wickham
R for Data Science (2nd edition) by Garrett Grolemund, Hadley Wickham, Mine Çetinkaya-Rundel
The Tidyverse Cookbook by Garrett Grolemund
R Markdown: The Definitive Guide by Yihui Xie, J. J. Allaire, Garrett Grolemund
Advanced R by Hadley Wickham
Cookbook for R by Winston Chang
R Graphics
Fundamentals of Data Visualization by Claus O. Wilke
R Graphics Cookbook (2nd edition) by Winston Chang
ggplot2: Elegant Graphics for Data Analysis by Hadley Wickham, Danielle Navarro, and Thomas Lin Pedersen.
R All-in-One Book
Big Book of R by Oscar Baruffa
Python Coding
Python Data Science Handbook by Jake VanderPlas
Fundamentals of Data Visualization by Claus O. Wilke
R Graphics Cookbook (2nd edition) by Winston Chang
R Basics: Quick and Easy - statistycal tools for data analysis and visualization, and quite a compact and quick-to-navigate R reference, exactly what's needed for simple guiding purposes
Coding Club R Course - a free and self-paced journey through a tailored selection of Coding Club tutorials, quizzes and practical challenges and the chance to get a certificate for your work
Useful links from Coding Club
Let’s Git started - great Git reference for R Studio