R: Access to and Manipulation of the Formal Arguments

formals {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

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