detach
Detach Objects from the Search Path
Detach a database, i.e., remove it from the search()
path of available R objects. Usually this is either a
data.frame
which has been attach
ed or a
package which was attached by library
.
- Keywords
- data
Usage
detach(name, pos = 2L, unload = FALSE, character.only = FALSE,
force = FALSE)
Arguments
- name
The object to detach. Defaults to
search()[pos]
. This can be an unquoted name or a character string but not a character vector. If a number is supplied this is taken aspos
.- pos
Index position in
search()
of the database to detach. Whenname
is a number,pos = name
is used.- unload
A logical value indicating whether or not to attempt to unload the namespace when a package is being detached. If the package has a namespace and
unload
isTRUE
, thendetach
will attempt to unload the namespace viaunloadNamespace
: if the namespace is imported by another namespace orunload
isFALSE
, no unloading will occur.- character.only
a logical indicating whether
name
can be assumed to be a character string.- force
logical: should a package be detached even though other attached packages depend on it?
Details
This is most commonly used with a single number argument referring to a
position on the search list, and can also be used with a unquoted or
quoted name of an item on the search list such as package:tools
.
If a package has a namespace, detaching it does not by default unload
the namespace (and may not even with unload = TRUE
), and
detaching will not in general unload any dynamically loaded compiled
code (DLLs). Further, registered S3 methods from the namespace will
not be removed. If you use library
on a package whose
namespace is loaded, it attaches the exports of the already loaded
namespace. So detaching and re-attaching a package may not refresh
some or all components of the package, and is inadvisable.
Value
The return value is invisible. It is NULL
when a
package is detached, otherwise the environment which was returned by
attach
when the object was attached (incorporating any
changes since it was attached).
Note
You cannot detach either the workspace (position 1) nor the base package (the last item in the search list), and attempting to do so will throw an error.
Unloading some namespaces has undesirable side effects: e.g.unloading grid closes all graphics devices, and on some systems tcltk cannot be reloaded once it has been unloaded and may crash R if this is attempted.
Good practice
detach()
without an argument removes the first item on the
search path after the workspace. It is all too easy to call it too
many or too few times, or to not notice that the search path has
changed since an attach
call.
Use of attach
/detach
is best avoided in functions (see
the help for attach
) and in interactive use and scripts
it is prudent to detach by name.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
attach
, library
, search
,
objects
, unloadNamespace
,
library.dynam.unload
.
Examples
library(base)
# NOT RUN {
require(splines) # package
detach(package:splines)
## or also
library(splines)
pkg <- "package:splines"
# }
# NOT RUN {
detach(pkg, character.only = TRUE)
## careful: do not do this unless 'splines' is not already attached.
library(splines)
detach(2) # 'pos' used for 'name'
## an example of the name argument to attach
## and of detaching a database named by a character vector
attach_and_detach <- function(db, pos = 2)
{
name <- deparse(substitute(db))
attach(db, pos = pos, name = name)
print(search()[pos])
detach(name, character.only = TRUE)
}
attach_and_detach(women, pos = 3)
# }
Community examples
```{r} library(ggplot2) detach("package:ggplot2") ```