[R] update.default evaluating in wrong environment?

[Thomas Lumley]

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