get {base}R Documentation

Return the Value of a Named Object

Description

Search by name for an object (get) or zero or more objects (mget).

Usage

get(x, pos = -1, envir = as.environment(pos), mode = "any",
    inherits = TRUE)

mget(x, envir = as.environment(-1), mode = "any", ifnotfound,
     inherits = FALSE)

dynGet(x, ifnotfound = , minframe = 1L, inherits = FALSE)

Arguments

x

For get, an object name (given as a character string or a symbol).
For mget, a character vector of object names.

pos, envir

where to look for the object (see ‘Details’); if omitted search as if the name of the object appeared unquoted in an expression.

mode

the mode or type of object sought: see the ‘Details’ section.

inherits

should the enclosing frames of the environment be searched?

ifnotfound

For mget, a list of values to be used if the item is not found: it will be coerced to a list if necessary.
For dynGet any R object, e.g., a call to stop().

minframe

integer specifying the minimal frame number to look into.

Details

The pos argument can specify the environment in which to look for the object in any of several ways: as a positive integer (the position in the search list); as the character string name of an element in the search list; or as an environment (including using sys.frame to access the currently active function calls). The default of -1 indicates the current environment of the call to get. The envir argument is an alternative way to specify an environment.

These functions look to see if each of the name(s) x have a value bound to it in the specified environment. If inherits is TRUE and a value is not found for x in the specified environment, the enclosing frames of the environment are searched until the name x is encountered. See environment and the ‘R Language Definition’ manual for details about the structure of environments and their enclosures.

If mode is specified then only objects of that type are sought. mode here is a mixture of the meanings of typeof and mode: "function" covers primitive functions and operators, "numeric", "integer" and "double" all refer to any numeric type, "symbol" and "name" are equivalent but "language" must be used (and not "call" or "("). Currently, mode = "S4" and mode = "object" are equivalent.

For mget, the values of mode and ifnotfound can be either the same length as x or of length 1. The argument ifnotfound must be a list containing either the value to use if the requested item is not found or a function of one argument which will be called if the item is not found, with argument the name of the item being requested.

dynGet() is somewhat experimental and to be used inside another function. It looks for an object in the callers, i.e., the sys.frame()s of the function. Use with caution.

Value

For get, the object found. If no object is found an error results. If the object is the internal missing argument (aka R_MissingArg in C), a classed error, class "getMissingError" is signalled.

For mget, a named list of objects (found or specified via ifnotfound).

Note

The reverse (or “inverse”) of a <- get(nam) is assign(nam, a), assigning a to name nam.

inherits = TRUE is the default for get in R but not for S where it had a different meaning.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

exists for checking whether an object exists; get0 for an efficient way of both checking existence and getting an object.

assign, the inverse of get(), see above.

Use getAnywhere for searching for an object anywhere, including in other namespaces, and getFromNamespace to find an object in a specific namespace.

Examples

get("%o%")

## test mget
e1 <- new.env()
mget(letters, e1, ifnotfound = as.list(LETTERS))

## very low-level: get()ing the "missing argument", e.g., inside browser()
ls.str(E <- environment((\(m) \(){})()))  # m : <missing>
str(E$m) # (empty) symbol
ee <- tryCatch(get("m",E), error = function(e) e)
str(ee)
ee
stopifnot(exprs = {
    inherits(ee, "missingArgError") # and
    inherits(ee, "getMissingError")
    ##
    inherits(tryCatch(get0("m", E), error=identity), "getMissingError")
    is.symbol(E$m) # => valid argument to get(), and *also* gets 'missing arg':
    inherits(tryCatch(get ( E$m ) , error=identity), "getMissingError")
})
[Package base version 4.5.0 Index]