Has anyone developed a version of do.call that is safe in the sense
that it silently drops parameters that do not appear in the formals of
the called function? This is useful when ... ends up being used in
multiple further functions. e.g.
f <- function(a, b) {a + b}
do.call(f, list(a=1, b=2, c=3)) # Errors
safe.call(f, list(a=1, b=2, c=3)) # Returns 3
If have quickly thrown together the following, but it doesn't support
position based calls, and I'd like to avoid reinventing the wheel.
safe.call <- function(f, params, f.params = names(formals(f))) {
if ("..." %in% f.params) {
safe.params <- params
} else {
safe.params <- params[intersect(f.params, names(params))]
}
do.call(f, safe.params)
}
I hope to use safe.call to prevent a wide class of potential bugs in ggplot2.
Hadley
--
http://had.co.nz/
Maybe this function won't actually be the help I had hoped it would be. Unfortunately some functions (e.g. glm via glm.control) throw errors when ... contain arguments that don't match some (eventual) argument list. Or is this a bug in glm? It certainly seems that the documentation should mention that ... is passed to glm.control, which only takes three arguments. I realise that this doesn't come up very often during an interactive model fitting session, and it is easy to remedy when it does, but it makes writing robust functions hard when a function with ... does in fact have a fixed argument list. Hadley On Jan 28, 2008 8:19 PM, hadley wickham <h.wickham at gmail.com> wrote:> Has anyone developed a version of do.call that is safe in the sense > that it silently drops parameters that do not appear in the formals of > the called function? This is useful when ... ends up being used in > multiple further functions. e.g. > > f <- function(a, b) {a + b} > do.call(f, list(a=1, b=2, c=3)) # Errors > safe.call(f, list(a=1, b=2, c=3)) # Returns 3 > > If have quickly thrown together the following, but it doesn't support > position based calls, and I'd like to avoid reinventing the wheel. > > safe.call <- function(f, params, f.params = names(formals(f))) { > if ("..." %in% f.params) { > safe.params <- params > } else { > safe.params <- params[intersect(f.params, names(params))] > } > do.call(f, safe.params) > } > > I hope to use safe.call to prevent a wide class of potential bugs in ggplot2. > > Hadley > > -- > http://had.co.nz/ >-- http://had.co.nz/
I tried to do this a couple of years ago, cf. doCall() in R.utils. It's quite a tricky problem and I recall I wasn't perfectly happy with the solution but it's a start. /Henrik On Jan 28, 2008 6:19 PM, hadley wickham <h.wickham at gmail.com> wrote:> Has anyone developed a version of do.call that is safe in the sense > that it silently drops parameters that do not appear in the formals of > the called function? This is useful when ... ends up being used in > multiple further functions. e.g. > > f <- function(a, b) {a + b} > do.call(f, list(a=1, b=2, c=3)) # Errors > safe.call(f, list(a=1, b=2, c=3)) # Returns 3 > > If have quickly thrown together the following, but it doesn't support > position based calls, and I'd like to avoid reinventing the wheel. > > safe.call <- function(f, params, f.params = names(formals(f))) { > if ("..." %in% f.params) { > safe.params <- params > } else { > safe.params <- params[intersect(f.params, names(params))] > } > do.call(f, safe.params) > } > > I hope to use safe.call to prevent a wide class of potential bugs in ggplot2. > > Hadley > > -- > http://had.co.nz/ > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >