[R] taking variables from data.frame

[MUGGEO VITO]

Dear all,
Two of the arguments of my function fn(), say, are a glm-obj and a variable
in the data.frame where there are the variable of the obj too.
Is there a way to build a function that takes the variables form the same
data.frame? For instance, the update() function does so:

>obj<-glm(....,data=mydata)
>update(obj,.~.+x) #works becuse it searches x in mydata

But for my function:
>fn(....,obj, mydata$x) #it works

and
>fn(....,obj, x) #doesn't works: x not found!

Of course I can attach the data.frame in the function by something like:

fn<-function(....,data){
 attach(data)
 ....
 detach()
 }

but is there anyone that can suggest me anything better?
Thank you very much for your help,
vito
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