R: How to run some code on load of package?

Question

I am learning to build a package for R. Now to set it up I need to run some code when the package is being loaded via require(myPackage).

I read the documentation on help(".onLoad") that just made me really confused as there is no example. How do I actually use .onLoad?

Can someone please show me a simple example? For example I know export(myfun) in the NAMESPACE file will export myfun for use, what is the code that I need to run say rnorm(10) at package load?

Answer 1

There is usually a "processing function" (traditionally called zzz.R) with tasks to be performed when the package is loaded, such as loading libraries and compiled code. For example you can create a zzz.R file where you create this function:

.onLoad <- function(libname, pkgname){
  x <- rnorm(10)   ## dummy example 
}

Answer 2

The R Packages ebook talks a bit more about using .onLoad() and .onAttach(): https://r-pkgs.org/r.html?q=onattach#when-you-do-need-side-effects