do.call

R Base 3.6.2

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

Syntax

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

Arguments

Parameter	Description
`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.

Return Value

The result of the (evaluated) function call.

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.

Examples

Example

# NOT RUN {
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
# }