How to unload a package without restarting R

Question

I'd like to unload a package without having to restart R (mostly because restarting R as I try out different, conflicting packages is getting frustrating, but conceivably this could be used in a program to use one function and then another--although namespace referencing is probably a better idea for that use).

?library doesn't show any options that would unload a package.

There is a suggestion that detach can unload package, but the following both fail:

detach(vegan) 

Error in detach(vegan) : invalid name argument

detach("vegan") 

Error in detach("vegan") : invalid name argument

So how do I unload a package?

Answer 1

Try this (see ?detach for more details):

detach("package:vegan", unload=TRUE) 

---

It is possible to have multiple versions of a package loaded at once (for example, if you have a development version and a stable version in different libraries). To guarantee that all copies are detached, use this function.

detach_package <- function(pkg, character.only = FALSE) {   if(!character.only)   {     pkg <- deparse(substitute(pkg))   }   search_item <- paste("package", pkg, sep = ":")   while(search_item %in% search())   {     detach(search_item, unload = TRUE, character.only = TRUE)   } } 

Usage is, for example

detach_package(vegan) 

or

detach_package("vegan", TRUE) 

Answer 2

You can also use the unloadNamespace command, as in:

unloadNamespace("sqldf") 

The function detaches the namespace prior to unloading it.