Re: [R] converting strings to expressions

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Thu 14 Sep 2006 - 20:35:27 GMT

Prof Brian Ripley <ripley@stats.ox.ac.uk> writes:

> On Thu, 14 Sep 2006, Deepayan Sarkar wrote:
>
> [...]
>
> > Ah, I'd forgotten about parse. A link from ?expression might be reasonable.
>
> But it says
>
> Details:
>
> 'Expression' here is not being used in its colloquial sense, that
> of mathematical expressions. Those are calls (see 'call') in R,
> and an R expression vector is a list of calls, typically as
> returned by 'parse'.
>
> so it already has a link.
>
> 'Expression' was often misused in the R documentation, and a couple of
> months ago I tried to move to a more careful usage.

Actually, you need to be even more careful because has commonly been called "unevaluated expressions" cover symbols and constants too. I.e., quote(1) and quote(x) are not calls. And such non-call objects can be elements of an expression vector.

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Fri Sep 15 06:38:52 2006

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