R currently supports two internal OOP systems (S3 and S4), and several others as add-on packages, such as R.oo, and OOP. S3 is easy to use but not reliable enough for large software projects. The emphasis of the S3 system was on generic functions and polymorphism. It’s a function centric system which is different to class centric system like...



Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).