| match.call | R Documentation |
match.call returns a call in which all of the specified arguments are
specified by their full names.
match.call(definition = sys.function(sys.parent()),
call = sys.call(sys.parent()),
expand.dots = TRUE,
envir = parent.frame(2L))
definition |
a function, by default the function from which
|
call |
an unevaluated call to the function specified by
|
expand.dots |
logical. Should arguments matching |
envir |
an environment, from which the |
‘function’ on this help page means an interpreted function
(also known as a ‘closure’): match.call does not support
primitive functions (where argument matching is normally
positional).
match.call is most commonly used in two circumstances:
To record the call for later re-use: for example most
model-fitting functions record the call as element call of
the list they return. Here the default expand.dots = TRUE
is appropriate.
To pass most of the call to another function, often
model.frame. Here the common idiom is that
expand.dots = FALSE is used, and the ... element
of the matched call is removed. An alternative is to
explicitly select the arguments to be passed on, as is done in
lm.
Calling match.call outside a function without specifying
definition is an error.
An object of class call.
Chambers, J. M. (1998) Programming with Data. A Guide to the S Language. Springer.
sys.call() is similar, but does not expand the
argument names;
call, pmatch, match.arg,
match.fun.
match.call(get, call("get", "abc", i = FALSE, p = 3))
## -> get(x = "abc", pos = 3, inherits = FALSE)
fun <- function(x, lower = 0, upper = 1) {
structure((x - lower) / (upper - lower), CALL = match.call())
}
fun(4 * atan(1), u = pi)
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