Re: [R] all.vars for nested expressions
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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Re: [R] all.vars for nested expressions
Hi Felix,
I thought, this could be an easy task for substitute, and the following
works as expected:
all.vars(substitute(expression(tp/a),list(a=expression(fn+tp
# [1] "tp" "fn"
But (of course)
all.vars(substitute(sen,list(a=a)))
does not yield the desired result, and I can't figure out, how to set up
as.name, bquote, eval, deparse etc to do the task properly.
Instead, my approach is a recursive call to all.vars
xall.help<-function(x){
#check if there is an object with name x
if(exists(x)) lapply(all.vars(get(x)),xall.help) else x}
xall.vars<-function(x){
if (!is.character(x)) x<-paste(substitute(x))
#for convenience put in a single vecotr
#xall.help returns a 'parsed tree'
unique(unlist(xall.help(x)))
}
#example
fn<-expression(n1+n2)
a <- expression(fn+tp)
sen <- expression(tp/a)
xall.vars(sen)
# [1] "tp" "n1" "n2"
cheers.
Am 29.04.2013 13:33, schrieb flxms:
> 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]]
>
> __
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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[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]] __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[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]] __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
