On Thu, Jun 27, 2013 at 8:49 PM, Ben Bolker <[email protected]> wrote:
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> The lmer() function in the lme4 package has some code of the form
>
> mc <- match.call()
> mc[[1]] <- as.name("lFormula")
> lmod <- eval(mc, parent.frame(1L))
>
> this is a fairly common idiom in R, found e.g. in lm(), used when
> one wants to pass all of the arguments of a function to a different
> function (in the case of lm() it's model.frame()).
>
I think the use of stack inspection ( usually parent.frame(), but with
match.call() often playing an accessory role) should be more widely
considered Evil, but I could get very off topic on that.
Passing along all the current function's arguments to another function is
implemented fairly well in S3 method dispatch. For example:
###
aMethod <- function(...) UseMethod("aMethod")
aMethod.default <- function(object, continue) {
if (continue) {
.Class <- "alternate"
NextMethod()
}
c("default", object)
}
aMethod.alternate <- function(object, continue) {
c("alternate", object)
}
x <- "this is the wrong x"
local({
x <- "this is the right x"
aMethod(x, TRUE)
})
###
Peter
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