How to unload a package without restarting R

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?

Solution 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)

Solution 2:

You can also use the unloadNamespace command, as in:

unloadNamespace("sqldf")

The function detaches the namespace prior to unloading it.

Solution 3:

You can uncheck the checkbox button in RStudio (packages).

Solution 4:

I tried what kohske wrote as an answer and I got error again, so I did some search and found this which worked for me (R 3.0.2):

require(splines) # package
detach(package:splines)

or also

library(splines)
pkg <- "package:splines"
detach(pkg, character.only = TRUE)