A Review of Scalable Bioinformatics Pipelines by Bjørn Fjukstad & Lars Ailo Bongo
This is one of the best tutorial by Fong Chun Chan
http://tinyheero.github.io/jekyll/update/2015/07/26/making-your-first-R-package.html
Notes/Blog by Hilary Parker is also very informative https://hilaryparker.com/2014/04/29/writing-an-r-package-from-scratch/