[R] Parsing for list components

Peter Dalgaard BSA
Thu, 18 Oct 2001 16:31:58 -0000

"G. Sawitzki" <gs at statlab.uni-heidelberg.de> writes:

> How do I parse an identifier of a list component, e.g.
> 	mylist$mycomponent
> or
> 	mylist[[1]] ?
> Parse does not do the job, e.g.
> 	parse(text="mylist$mycomponent")
> returns an expression with just one term, instead of "mylist",
"$",
> "mycomponent".
>
> What I need is a way to extract the list name (e.g. "mylist"),
given
> an identifier of a component. Splitting the string is possible, but I
> think there are better solutions.

parse() *does* do the job:

> parse(text="mylist$mycomponent")[[1]][[2]]
mylist

or maybe

> as.character(parse(text="mylist$mycomponent")[[1]][[2]])
[1] "mylist"

I.e., you just need to pick the result apart afterwards.

--
   O__  ---- Peter Dalgaard             Blegdamsvej 3
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
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