match.call {base} | R Documentation |
match.call
returns a call in which all of the specified arguments are
specified by their full names.
match.call(definition = NULL, call = sys.call(sys.parent()),
expand.dots = TRUE)
definition |
a function, by default the function from which
|
call |
an unevaluated call to the function specified by
|
expand.dots |
logical. Should arguments matching |
‘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 ...
elememt
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)