R: Execute a Function Call

do.call {base} | R Documentation

## Execute a Function Call

### Description

`do.call` constructs and executes a function call from a name or a function and a list of arguments to be passed to it.

### Usage

    do.call(what, args, quote = FALSE, envir = parent.frame())

### Arguments

`what` | either a function or a non-empty character string naming the function to be called.
`args` | a list of arguments to the function call. The `names` attribute of `args` gives the argument names.
`quote` | a logical value indicating whether to quote the arguments.
`envir` | an environment within which to evaluate the call. This will be most useful if `what` is a character string and the arguments are symbols or quoted expressions.

### Details

If `quote` is `FALSE`, the default, then the arguments are evaluated (in the calling environment, not in `envir`). If `quote` is `TRUE` then each argument is quoted (see `quote`) so that the effect of argument evaluation is to remove the quotes – leaving the original arguments unevaluated when the call is constructed.

The behavior of some functions, such as `substitute`, will not be the same for functions evaluated using `do.call` as if they were evaluated from the interpreter. The precise semantics are currently undefined and subject to change.

### Value

The result of the (evaluated) function call.

### References

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

### See Also

`call` which creates an unevaluated call.

### Examples

    do.call("complex", list(imag = 1:3))

    ## if we already have a list (e.g. a data frame)
    ## we need c() to add further arguments
    tmp <- expand.grid(letters[1:2], 1:3, c("+", "-"))
    do.call("paste", c(tmp, sep=""))

    do.call(paste, list(as.name("A"), as.name("B")), quote=TRUE)

    ## examples of where objects will be found.
    A <- 2
    f <- function(x) print(x^2)
    env <- new.env()
    assign("A", 10, envir = env)
    assign("f", f, envir = env)
    f <- function(x) print(x)
    f(A)                                    # 2
    do.call("f", list(A))                   # 2
    do.call("f", list(A), envir=env)        # 4
    do.call(f, list(A), envir=env)          # 2
    do.call("f", list(quote(A)), envir=env) # 100
    do.call(f, list(quote(A)), envir=env)   # 10
    do.call("f", list(as.name("A")), envir=env) # 100

    eval(call("f", A))                      # 2
    eval(call("f", quote(A)))               # 2
    eval(call("f", A), envir=env)           # 4
    eval(call("f", quote(A)), envir=env)    # 100

[Package base version 2.15.1 Index]