match.call

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Argument Matching

match.call returns a call in which all of the specified arguments are specified by their full names.

Keywords
programming
Usage
match.call(definition = sys.function(sys.parent()), call = sys.call(sys.parent()), expand.dots = TRUE, envir = parent.frame(2L))
Arguments
definition
a function, by default the function from which match.call is called. See details.
call
an unevaluated call to the function specified by definition, as generated by call.
expand.dots
logical. Should arguments matching ... in the call be included or left as a ... argument?
envir
an environment, from which the ... in call are retrieved, if any.
Details

‘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.

    Value

    An object of class call.

    References

    Chambers, J. M. (1998) Programming with Data. A Guide to the S Language. Springer.

    See Also

    sys.call() is similar, but does not expand the argument names; call, pmatch, match.arg, match.fun.

    Aliases
    • match.call
    Examples
    library(base) 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)
    Documentation reproduced from package base, version 3.2.0, License: Part of R 3.2.0

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