Expanding partial names
On 3/7/06, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
I'm writing wrappers for some functions that change some of the default
arguments. I'd rather not list all of the arguments for the low level
functions because there are about a dozen wrapper functions, and about
20 arguments to lowlevel. Instead I'm trying something like this:
lowlevel <- function(longname = 1) {
cat("longname = ", longname, "\n")
}
wrapper <- function(...) {
newargs <- list(longname = 2)
newargs[names(list(...))] <- list(...)
do.call("lowlevel", newargs)
}
This almost works:
> wrapper()
longname = 2
> wrapper(longname = 3)
longname = 3 But it fails if I try to use partial argument matching:
> wrapper(long=4)
Error in lowlevel(longname = 2, long = 4) :
unused argument(s) (long ...)
because long isn't matched to longname. Is there a reasonable way to do
this (e.g. using pmatch or charmatch) other than listing all the low
level arguments in the argument list to wrapper?
One trick I often use that is different from any of the suggestions I have seen so far (and is more transparent IMO) is the following:
lowlevel <- function(longname = 1) {
cat("longname = ", longname, "\n")
}
wrapper <- function(...) {
newArgs <-
function(longname = 2, ...)
list(longname = longname,
...)
do.call("lowlevel", newArgs(...))
}
which gives:
wrapper()
longname = 2
wrapper(longname = 3)
longname = 3
wrapper(long=20)
longname = 20
wrapper(junk=3)
Error in lowlevel(longname = 2, junk = 3) : unused argument(s) (junk ...) -Deepayan