| formals | R Documentation |
Get or set the formal arguments of a function.
formals(fun = sys.function(sys.parent()), envir = parent.frame()) formals(fun, envir = environment(fun)) <- value
fun |
a |
envir |
|
value |
a |
For the first form, fun can also be a character string naming
the function to be manipulated, which is searched for in envir,
by default from the parent
frame. If it is not specified, the function calling formals is
used.
Only closures have formals, not primitive functions.
formals returns the formal argument list of the function
specified, as a pairlist, or NULL for a
non-function or primitive.
The replacement form sets the formals of a function to the
list/pairlist on the right hand side, and (potentially) resets the
environment of the function, dropping attributes.
formalArgs (from methods), a shortcut for names(formals(.)).
args for a human-readable version,
alist to construct a typical formals value,
see the examples.
The three parts of a (non-primitive) function are its
formals, body, and environment.
require(stats) formals(lm) ## If you just want the names of the arguments, use formalArgs instead. names(formals(lm)) methods:: formalArgs(lm) # same ## formals returns a pairlist. Arguments with no default have type symbol (aka name). str(formals(lm)) ## formals returns NULL for primitive functions. Use it in combination with ## args for this case. is.primitive(`+`) formals(`+`) formals(args(`+`)) ## You can overwrite the formal arguments of a function (though this is ## advanced, dangerous coding). f <- function(x) a + b formals(f) <- alist(a = , b = 3) f # function(a, b = 3) a + b f(2) # result = 5
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