[R] Dots in models formulae

[Sundar Dorai-Raj]

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