On Thu, 19 May 2011, Liaw, Andy wrote:
From: Prof Brian Ripley
Hmm, load() does have an 'envir' argument. So you could simply use
that and with() (which is pretty much what attach() does internally).
If people really wanted a lazy approach, with() could be extended to
allow file names (as attach does).
I'm not sure if laziness like this should be encouraged.
As you can tell from my wording, I was not (and indeed consider the
change to attach() to accept .rda files to have been a mistake).
If I may bring up another "black hole": IMHO the formula interface
allows too much flexibility (perhaps to allow some laziness?) that
beginners and even non-beginners fall into its various traps a bit too
often, and sometimes not even aware of it. It would be great if there's
a way to (optionally?) limit the scope of where a formula looks for
variables.
Note, there is no such thing as 'the formula interface'. There are
several, but I expect you mean model.frame.default, for that is what
is most commonly used to collect together the variables from which to
interpret a formula. Now in my view model.frame suffers from having
been designed for S's scoping rules and subverted for R by users of
lexical scoping. So it has to work for both approaches (or break even
more legacy code than the 1.2.0 changes did). In my experience the
most common trap is to pick up variables in the workspace when 'data'
(or 'newdata') is supplied, and that is unavoidable if you allow
lexical scoping as the workspace is almost always in the environment
of the formula. You can change the latter of course, but I suspect
that in 99.9% of cases if a user supplies 'data' he intends to get all
the variables from 'data'.
This is not really the place for such a disussion, so if you want to
pursue it please restart it on R-devel.
Just my $0.02...
Andy
On Thu, 19 May 2011, Martin Maechler wrote:
[modified 'Subject' on purpose;
Good mail readers will still thread correctly, using the
'References'
and 'In-Reply-To' headers, however, unfortunately,
in my limited experience, good mail readers seem to
disappear more and more ..
]
Peter Ehlers <ehl...@ucalgary.ca>
on Tue, 17 May 2011 06:08:30 -0700 writes:
> On 2011-05-17 02:22, Timothy Bates wrote:
>> Dear Bryony: the suggestion was not to change the name of
>> the data object, but to explicitly tell glm.nb what
>> dataset it should look in to find the variables you
>> mention in the formula.
>>
>> so the salient difference is:
>>
>> m1<- glm.nb(Cells ~ Cryogel*Day, data = side)
>>
>> instead of
>>
>> attach(side) m1<- glm.nb(Cells ~ Cryogel*Day)
>>
>> This works for other functions also, but not uniformly as
>> yet (how I wish it did and I could say hist(x, data=side)
>> Instead of hist(side$x)
>>
>> this inconsistency encourages the need for attach()
> Only if the user hasn't yet been introduced to the with()
> function, which is linked to on the ?attach page.
> Note also this sentence from the ?attach page:
> ".... attach can lead to confusion."
> I can't remember the last time I needed attach().
> Peter Ehlers
Well, then you don't know *THE ONE* case where modern users of
R should use attach() ... as I have been teaching for a while,
but seem not have got enought students listening ;-) ...
--- Use it instead of load() {for save()d R objects} ---
The advantage of attach() over load() there is that loaded
objects (and there maye be a bunch!), are put into a separate
place in the search path and will not accidentally overwrite
objects in the global "workspace".
Of course, there are still quite a few situations {e.g. in
typical BATCH use of R for simulations, or Sweaving, etc} where
load() is good enough, and the extras of using attach() are not
worth it.
But the unconditional "do not use attach()"
is not quite ok,
at least not when you talk to non-beginners.
Martin Maechler, ETH Zurich
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
