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))a function, by default the function from which
match.call is called. See details.
an unevaluated call to the function specified by
definition, as generated by call.
logical. Should arguments matching …
in the call be included or left as a … argument?
an environment, from which the … in call
are retrieved, if any.
An object of class call.
‘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.
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.
# NOT RUN {
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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