[R] lm: eval(parse(text=)) works on one side y/x but not on both?

[Matthieu Stigler]

Thanks for answering so fast!!
>
>    lm(freeny)
:-)
Ok that's working for the one equation case :-) Was example case...

But now I want to have not only first column of freeny on the left but 
both first? And I don't know their names a priori...

Thanks!
>
> On Sun, Nov 29, 2009 at 8:49 AM, Matthieu Stigler 
> <matthieu.stigler at gmail.com <mailto:matthieu.stigler at gmail.com>> wrote:
>
>     Hi
>
>     My goal is to do a (multiple) regression, just knowing that my Y
>     variables will be the say k first variables of a matrix/data
>     frame. I thought I should do it with eval(parse)) but encounter a
>     strange problem.
>
>     See:
>     lm(y~.-y, data=freeny) #that's what I want to do in the one
>     equation case
>     #Problem is I don't know name of the variable... only that it is
>     the first one...
>     #so idea is to just take first name
>     a<-colnames(freeny)
>     #and then use eval(parse(text=a[1]))
>
>     #it works if I replace y on either the left or right side:
>     lm(eval(parse(text=a[1]))~.-y, data=freeny) #does the same
>     lm(y~.-eval(parse(text=a[1])), data=freeny)
>
>     #but not if I do this call twice:
>     lm(eval(parse(text=a[1]))~.-eval(parse(text=a[1])), data=freeny)
>     #variable I wanted to remove (y) ist still there
>
>     Do you understand why I can call eval(parse) only once? Should I
>     try a update workaround? Or have idea of any other solution? Maybe
>     there is something much simpler I'm missing:-(
>
>     Thanks a lot!!!
>
>     Matthieu Stigler
>
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