[R] meaning of lm( y~., data=mydat ), is it a language feature, is it documented, is it supported?

[Ivan Calandra]

Hi John,

This is indeed documented, but you'll have to look at the function 
formula():
?formula

Regarding the dot (.), here is the explanation from the help of formula():
"There are two special interpretations of . in a formula. The usual one 
is in the context of a data argument of model fitting functions and 
means ‘all columns not otherwise in the formula’: see terms.formula. In 
the context of update.formula, only, it means ‘what was previously in 
this part of the formula’."

HTH,
Ivan

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Le 23/05/2016 à 13:26, John Sorkin a écrit :
>   
> The syntax
> mydat <- data.frame( y,x )
> fit1 <- lm( y~., data=mydat )
> appears to perform a multivariable regression of y on every non-y variable in the data frame mydat. I can not find this syntax (y~.) in R documentation. Is y~. a supported feature of the R language? Where can I find it documented? I would hate to write code that is dependent on a non-supported, non-documented language feature.
> Thank you,
> John
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
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