On Nov 23, 2011, at 00:24 , Rolf Turner wrote:
>>
>> library(fortunes)
>> fortune("parse()")
> The fortune notwithstanding I find this *specific* use of parse() to be
> very, uh, useful! :-)
The fortune does say "usually", and there certainly are exceptions, for
instance the use in Rcmdr where you edit and submit code from the log window.
What to avoid is something like this:
value <- 3.2; r <- 1
cmd <- paste("pexp(",value,",rate=",r,")")
eval(parse(text=cmd))
where
pexp(value,rate=r)
would do. Or, if you do need the unevaluated expression:
bquote(pexp(.(value),rate=.(r)))
(I believe we still have a couple of cases in the standard R code where the
code does something like
rhs <- paste(vnames, sep="+")
and then proceeds to parse it and put the result into the right hand side of a
model formula. It works (mostly) but it hurts my eyes seeing computing on the
language done via the textual representation.)
--
Peter Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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