[R] Dots in models formulae

[Gavin Simpson]

On Tue, 2005-08-16 at 12:24 -0500, Sundar Dorai-Raj wrote:
> 
> Uwe Ligges wrote:
> > Laurent Valdes wrote:
> > 
> > 
> >>I have seen, several times, dots (like this: "y ~." ) in formula  
> >>descriptions, noticeably in R help.
> >>
> >>I am unable to see what it does correspond to.
> >>
> >>Any ideas ?
> > 
> > 
> > All other variables (except y) from the given data.frame...
> > 
> > Uwe Ligges
> > 
> 
> Hi, Uwe,
> 
> Doesn't this depend on the context? For example,
> 
> z <- data.frame(y = rnorm(10), x = rnorm(10))
> fit <- lm(y ~ ., z)
> update(fit, y ~ . + I(x^2))
> 
> The original poster did not say where he saw this formula. However, I 
> think the reference in ?formula has the most authorative explanation.

Not for "." in a formula in ?formula, at least in 

platform i686-pc-linux-gnu
arch     i686
os       linux-gnu
system   i686, linux-gnu
status   Patched
major    2
minor    1.1
year     2005
month    08
day      15
language R

I still can't find this documented for a formula (I found
update.formula, but the meaning of "." is different there, slightly, as
you indicate) - but it must be as I didn't imagine seeing it - or maybe
I did...

G

> Thanks,
> 
> --sundar
> 
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Gavin Simpson                     [T] +44 (0)20 7679 5522
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