R help - Nov 2006 - difference in using with() and the "data" argument in glm call

Dear all,
I am dealing with the following (apparently simple problem):
For some reasons I am interested in passing variables from a dataframe 
to a specific environment, and in fitting a standard glm:

dati<-data.frame(y=rnorm(10),x1=runif(10),x2=runif(10))
KK<-new.env()
for(i in 1:ncol(dati)) assign(names(dati[i]),dati[[i]],envir=KK)
#Now the following two lines work correctly:
coef(glm(y~x1+x2,data=KK))
with(KK,coef(glm(y~x1+x2)))

#However if I write the above code inside a function, with() does not 
appear to work..

ff<-function(Formula,Data,method=1){
     KK<-new.env()
     for(i in 1:ncol(Data)) assign(names(Data[i]),Data[[i]],envir=KK)
     o<-if(method==1) glm(Formula,data=KK) else with(KK,glm(Formula))
     o}

 > ff(y~x1+x2,dati,1) #it works
Call:  glm(formula = Formula, data = KK)
..[SNIP]..
 > ff(y~x1+x2,dati,2) #it does not
Error in eval(expr, envir, enclos) : object "y" not found
 >

Could anyone to explain such difference? I believed that
"with(data,glm(formula))" and "glm(formula,data)" were
equivalent.

Many thanks,
vito



-- 
===================================Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
Universit? di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 6626240
fax: 091 485726/485612

It looks into the data argument first and if not found there it looks into
environment(formula).  Thus to pick it out of the 'with' try this:

with(KK, glm(fo, data = environment())

Also you could try this:

environment(fo) <- KK
glm(fo)


On 11/3/06, vito muggeo <vmuggeo at dssm.unipa.it>
wrote:
> Dear all,
> I am dealing with the following (apparently simple problem):
> For some reasons I am interested in passing variables from a dataframe
> to a specific environment, and in fitting a standard glm:
>
> dati<-data.frame(y=rnorm(10),x1=runif(10),x2=runif(10))
> KK<-new.env()
> for(i in 1:ncol(dati)) assign(names(dati[i]),dati[[i]],envir=KK)
> #Now the following two lines work correctly:
> coef(glm(y~x1+x2,data=KK))
> with(KK,coef(glm(y~x1+x2)))
>
> #However if I write the above code inside a function, with() does not
> appear to work..
>
> ff<-function(Formula,Data,method=1){
>     KK<-new.env()
>     for(i in 1:ncol(Data)) assign(names(Data[i]),Data[[i]],envir=KK)
>     o<-if(method==1) glm(Formula,data=KK) else with(KK,glm(Formula))
>     o}
>
>  > ff(y~x1+x2,dati,1) #it works
> Call:  glm(formula = Formula, data = KK)
> ..[SNIP]..
>  > ff(y~x1+x2,dati,2) #it does not
> Error in eval(expr, envir, enclos) : object "y" not found
>  >
>
> Could anyone to explain such difference? I believed that
> "with(data,glm(formula))" and "glm(formula,data)" were
equivalent.
>
> Many thanks,
> vito
>
>
>
> --
> ===================================> Vito M.R. Muggeo
> Dip.to Sc Statist e Matem `Vianelli'
> Universit? di Palermo
> viale delle Scienze, edificio 13
> 90128 Palermo - ITALY
> tel: 091 6626240
> fax: 091 485726/485612
>
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