Introduction Because R is, in part, a functional programming language, the ‘base’ package contains several higher order functions. By higher order functions, I mean functions that take another function as an argument and then do something with that function. If you want to know more about the usefulness of writing higher order functions in general,









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