Message-ID: <43022155.5090901@pdf.com>
Date: 2005-08-16T17:24:37Z
From: Sundar Dorai-Raj
Subject: Dots in models formulae
In-Reply-To: <43021F7D.9030300@statistik.uni-dortmund.de>
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.
Thanks,
--sundar