Try poking around in the codetools package. E.g., you can do things like the
following
expr1 <- quote(a <- fn + tp) # put 'a' in the expression
expr2 <- quote( tp / a + fn)
expr12 <- call("{", expr1, expr2)
expr12
# {
# a <- fn + tp
# tp/a + fn
# }
library(codetools)
findLocals(expr12) # from codetools
# [1] "a"
setdiff(all.vars(expr12), findLocals(expr12))
# [1] "fn" "tp"
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of flxms
> Sent: Monday, April 29, 2013 4:34 AM
> To: r-help@r-project.org
> Subject: [R] all.vars for nested expressions
>
> Dear R fellows,
>
> Assume I define
>
> a <- expression(fn+tp)
> sen <- expression(tp/a)
>
> Now I'd like to know, which variables are necessary for calculating sen
>
> all.vars(sen)
>
> This results in a vector c(tp,a). But I'd like all.vars to evaluate the
> sen-object down to the ground level, which would result in a vector
> c(tp,fn) (because a was defined as fn+tp). In other words, I'd like
> all.vars to expand the a-object (and all other downstream objects). I am
> looking for a solution, that works with much more levels. This is just a
> very simple example.
>
> I'd appreciate any suggestions how to do that very much!
> Thanks in advance,
>
> Felix
>
> [[alternative HTML version deleted]]
>
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