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

6 messages · John Sorkin, Duncan Murdoch, Ivan Calandra +3 more

John Sorkin
# 
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
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Duncan Murdoch
#
On 23/05/2016 7:26 AM, John Sorkin wrote:
It is documented in the Introduction to R manual (hidden in section 
11.5, "Updating fitted models"), and in ?formula, which ?lm refers to.

Duncan Murdoch
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 ? 13:26, John Sorkin a ?crit :
Ken Knoblauch
# 
John Sorkin <JSorkin <at> grecc.umaryland.edu> writes:
every non-y variable in the data frame mydat. I can not
a supported feature of the R language? Where can I find it
is dependent on a non-supported, non-documented 
language feature.
Medicine Division of Gerontology and Geriatric Medicine
How about section 11.5 of An Introduction to R?
Bert Gunter
# 
It's about formula syntax, so ?formula documents it.

Bert
On Monday, May 23, 2016, John Sorkin <JSorkin at grecc.umaryland.edu> wrote:

            

      
      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Peter Dalgaard
    

    

      
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Actually, it is debatable which one of those deserve to be called "usual". Once upon a time, in the heyday of John Tukey, it might have been usual to have data set of a few hundred rows and, like, a dozen columns, exactly one of which being the response. Not so much these days, I'd say.

-pd