formals                 package:base                 R Documentation

Access to and Manipulation of the Formal Arguments

Description:

     Get or set the formal arguments of a function.

Usage:

     formals(fun = sys.function(sys.parent()))
     formals(fun) <- list

Arguments:

     fun: a function object or a character string naming the function
          to be manipulated. If not specified, the function calling
          `body' is used.

    list: a list of R expressions.

Value:

     `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'.

Examples:

     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

