[R] Optional arguments in stats::nls
murdoch.duncan at gmail.com
Tue Feb 28 20:08:37 CET 2017
On 28/02/2017 11:07 AM, Rytis Bagdziunas wrote:
> Hello everyone,
> I've been struggling with the usage of ellipsis argument for stats::nls
> and similar functions. In particular, nls manual indicates this:
> ...: Additional optional arguments. None are used at present.
The documentation is incorrect.
> However, "none are used" seems to be slightly misleading. Here's an
> data <- data.frame("x" = rnorm(100),
> "y" = rnorm(100))
> fn <- function(y, a) a * y
> ## This works
> nls(y ~ fn(x, a), data = data, start = list("a" = 1))
> ## This doesn't
> nls(y ~ fn(x, a), data = data, start = list("a" = 1), myarg = FALSE)
> ## But this does
> nls(y ~ fn(x, a), data = data, start = list("a" = 1), myarg = rnorm(100))
> traceback() indicates that the additional argument is passed to
> model.frame.default() but doesn't appear to do anything.
> Is this expected behaviour?
The docs should say "...: additional arguments that may be passed to
Likely the reason the docs are wrong is that the call to model.frame is
put together in a tricky way, using match.call(), and it's not so
obvious what the conditions are under which it will be called. I don't
see a simple fix to the docs other than what I wrote above.
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