Re: [Rd] messing with ...

From: Christos Hatzis <christos.hatzis_at_nuverabio.com>
Date: Wed, 13 Aug 2008 12:38:27 -0400

If I understand it correctly, one way would be to define a function to specify the default options/arguments in the required order.

For example,

> mle.options <- function(method = "BFGS", lower = 0, upper = Inf,
hessian=FALSE)
+ list(method=method, lower=lower, upper=upper, hessian=hessian)
> mle.options()

$method
[1] "BFGS" $lower
[1] 0

$upper
[1] Inf

$hessian
[1] FALSE And the user can specify only the parameters that need non-default values:

> mle.options(method="CG")

$method
[1] "CG"

$lower
[1] 0

$upper
[1] Inf

$hessian
[1] FALSE A similar function can be defined for the control parameters of optim. Then all you need in the mle wrapper is:

mle <- function(X, Y, optim.meth=mle.options(), optim.control=mle.control(), ...) {

        # preparatory steps         

	optim(par, fn, method=optim.meth$method, lower=optim.meth$lower, 
		upper=optim.meth$upper, hessian=optim.meth$hessian,
		control = optim.control(), ...)

	# more stuff

}

Hope this helps.

-Christos

> -----Original Message-----
> From: r-devel-bounces_at_r-project.org
> [mailto:r-devel-bounces_at_r-project.org] On Behalf Of Ben Bolker
> Sent: Wednesday, August 13, 2008 11:46 AM
> To: r-devel_at_r-project.org
> Subject: [Rd] messing with ...
>
>
> I'm looking for advice on manipulating parameters that are
> going to be passed through to another function.
>
> Specifically, I am working on my version of "mle", which
> is a wrapper for optim (among other optimizers).
> I would prefer not to replicate the entire argument list of
> optim(), so I'm using ... to pass extra arguments through.
>
> However:
> the starting values are specified as a list, which means
> that users can potentially specify them in any order (or at
> least that's the way it works now -- one solution to the
> problem I'm about to state is to insist that they specify the
> parameters in the same order as they are given in the
> arguments of the objective function).
> However, there are other arguments (lower, upper,
> control$parscale, control$ndeps) that should all be in the
> same order as the objective function definition by the time
> they get to optim()). I can think of a few solutions:
>
> (1) make the user specify them all in the right order (ugh)
> (2) add all of them as explicit parameters to my function
> so that I can rearrange them appropriately (ugh)
> (3) mess with the ... argument before it gets passed
> through to optim (impossible?)
> (4) capture ... as arglist <- list(...), manipulate the
> arguments as necessary, then pass them along to optim as
> do.call("optim",arglist) (ugh but maybe the best solution?)
>
> any thoughts?
>
> thanks
>

> Ben Bolker
>
>
>



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