Re: [R] update.default evaluating in wrong environment?

From: Thomas Lumley <tlumley_at_u.washington.edu>
Date: Tue 10 Oct 2006 - 18:52:30 GMT

On Tue, 10 Oct 2006, Martin C. Martin wrote:
> Thanks, or even just:
>
> e <- environment(formula(f.lm))
>
> But this was more of a bug report. Is update.default wrong? Should it
> be changed? I don't see how evaluating in update's parent environment
> would ever be better default behavior than the formula's environment.
>

This is deliberate (although that doesn't necessarily imply that it is optimal). There already is a bug report (PR#1861) on this issue, so another one certainly isn't appropriate.

The comments for this bug report give an example taken from the scripts for MASS chapter 6, doing a bootstrap of a linear model ph.fun <- function(data, i) {

   d <- data
   d$calls <- d$fitted + d$res[i]
   coef(update(fit, data=d))
}

This is not uncommon for resampling and other perturbations of a model and requires looking in the calling frame of update().

For other uses such as yours the right place would be the frame where the model was created. Neither the environment of the formula nor the calling frame of update() is guaranteed to be the right place and it is easy to come up with examples where each works and the other doesn't.

There really isn't a trivial solution to this.

         -thomas



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