On 19/05/2011 10:34 AM, 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.
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.
I think there is: put the variables in an environment that doesn't have
parents covering everything visible, and use that as the environment of
the formula.
For example, you could follow
x <- 1:10
y <- rnorm(10)
z <- rnorm(10)
f <- y ~ x + z
with
e <- new.env(parent=baseenv())
e$x <- x
e$y <- y
environment(f) <- e
and you'll get a failure with
lm(f)
because it can't find z. Obviously this could be wrapped in a
friendlier function if you really wanted it.
Duncan Murdoch
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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