Inconsistent messages with [[ list indexing (PR#359)
ripley@stats.ox.ac.uk
ripley@stats.ox.ac.uk
Sat, 4 Dec 1999 15:16:01 +0100 (MET)
R 0.90.0:
> Empl <- list(aa=1, b=2, c=3)
> Empl[[as.numeric(NA)]]
Error in Empl[[as.numeric(NA)]] : subscript out of bounds
> Empl[[as.integer(NA)]]
Error: attempt to select more than one element
> Empl[[as.logical(NA)]]
Error: attempt to select more than one element
Now,
(a) None of those messages is appropriate.
(b) At least the first two should be the same.
(c) S gives NULL in each case.
Is there any reason not to follow S here? If so, I would prefer a
specific error message (`NA cannot be used to select a list element').
The usage
Empl[[ match("a", names(Empl)) ]]
is a very convenient one to defeat partial matching, but the current
behaviour of R defeats it. OK,
Empl[ match("a", names(Empl)) ] [[1]]
works, but this is an ugly hack (and the answer should I believe be the
same as [[ ]]).
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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