formals {base}R Documentation

Access to and Manipulation of the Formal Arguments


Get or set the formal arguments of a function.


formals(fun = sys.function(sys.parent()))
formals(fun, envir = parent.frame()) <- value


fun a function object, or see Details.
envir environment in which the function should be defined.
value a list of R expressions.


For the first form, fun can be a character string naming the function to be manipulated, which is searched for from the parent environment. If it is not specified, the function calling formals is used.


formals returns the formal argument list of the function specified.
The assignment form sets the formals of a function to the list on the right hand side.

See Also

args for a “human-readable” version, alist, body, function.


length(formals(lm))      # the number of formal arguments
names(formals(boxplot))  # formal arguments names

f <- function(x)a+b
formals(f) <- alist(a=,b=3) # function(a,b=3)a+b
f(2) # result = 5

[Package base version 2.1.0 Index]