| environment {base} | R Documentation |
Get, set, test for and create environments.
environment(fun = NULL) environment(fun) <- value is.environment(obj) .GlobalEnv globalenv() .BaseNamespaceEnv baseenv() new.env(hash = FALSE, parent = parent.frame()) parent.env(env) parent.env(env) <- value
fun |
a function, a formula, or
NULL, which is the default. |
value |
an environment to associate with the function |
obj |
an arbitrary R object. |
hash |
a logical, if TRUE the environment will be hashed |
parent |
an environment to be used as the enclosure of the environment created. |
env |
an environment |
Environments consist of a frame, or collection of named
objects, and a pointer to an enclosing environment. The most
common example is the frame of variables local to a function call;
its enclosure is the environment where the function was
defined. The enclosing environment is distinguished from the
parent frame: the latter (returned by
parent.frame) refers to the environment of the caller
of a function.
When get or exists search an environment
with the default inherits = TRUE, they look for the variable
in the frame, then in the enclosing frame, and so on.
The global environment .GlobalEnv, more often known as the
user's workspace, is the first item on the search path. It can also
be accessed by globalenv(). On the search path, each item's
enclosure is the next item.
The object .BaseNamespaceEnv is the namespace environment for
the base package. The environment of the base package itself is
available as baseenv(), currently NULL, the ultimate enclosure of any environment:
If one follows the parent.env() chain of enclosures back far
enough from any environment, eventually one reaches baseenv().
This means that arithmetic operators and the base package functions
will be always be found by eval() or get(...,
inherits = TRUE).
The replacement function parent.env<- is extremely dangerous as
it can be used to destructively change environments in ways that
violate assumptions made by the internal C code. It may be removed
in the near future.
is.environment is generic: you can write methods to handle
specific classes of objects, see InternalMethods.
If fun is a function or a formula then environment(fun)
returns the environment associated with that function or formula.
If fun is NULL then the current evaluation environment is
returned.
The assignment form sets the environment of the function or formula
fun to the value given.
is.environment(obj) returns TRUE iff obj is an
environment.
new.env returns a new (empty) environment enclosed in the
parent's environment, by default.
parent.env returns the parent environment of its argument.
parent.env<- sets the enclosing environment of its first
argument.
The envir argument of eval, get,
and exists.
ls may be used to view the objects in an environment.
##-- all three give the same:
environment()
environment(environment)
.GlobalEnv
ls(envir=environment(approxfun(1:2,1:2, method="const")))
is.environment(.GlobalEnv) # TRUE
e1 <- new.env(parent = baseenv()) # this one has enclosure package:base.
e2 <- new.env(parent = e1)
assign("a", 3, env=e1)
ls(e1)
ls(e2)
exists("a", env=e2) # this succeeds by inheritance
exists("a", env=e2, inherits = FALSE)
exists("+", env=e2) # this succeeds by inheritance