R: Execute a Function Call (original) (raw)
| do.call {base} | R Documentation |
|---|
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. Thenames 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). Ifquote is TRUE then each argument is quoted (see[quote](../../base/help/quote.html)) 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](../../base/help/substitute.html), 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.
Warning
This should not be used to attempt to evade restrictions on the use of.Internal and other non-API calls.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)The New S Language. Wadsworth & Brooks/Cole.
See Also
[call](../../base/help/call.html) which creates an unevaluated call.
Examples
do.call("complex", list(imaginary = 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 4.6.0 Index]