问题:

is there any way to display a message when a user loads library(myCustomLibrary)? Upon loading, I want to display a message that tells the user how to run all the test functions.

回答1:

Yes. You can use the .onLoad, .onAttach, or .First.lib functions to do whatever you want when the package is loaded. I suggest looking at the help for those functions. You would use .onLoad with a namespace, and .First.lib without.

One convention is that people will frequently put these commands in a separate zzz.R file, which is just used for package related code.

回答2:

Quick points:

if your package has a NAMESPACE, then .onLoad() is where you do this
if your package does not have NAMESPACE, then .First.lib() is where you do this
either way, use packageStartupMessage() instead of cat() so that users have a choice of suppressing this.