[Rd] Subsetted 1-D arrays (PR#4110)
Prof Brian Ripley
ripley at stats.ox.ac.uk
Wed Oct 22 08:54:48 MEST 2003
On Tue, 21 Oct 2003, David Brahm wrote:
> In R-patched_2003-10-20, subsetted 1-D arrays no longer get converted to
> vectors. The NEWS file documents this change, as an indirect result of bug
> report 4110. I just wanted to mention this can break code in some rather
> obscure ways, such as this toy example:
> R> x <- sort(tapply(1:8, rep(1:4,2), sum)) # Was vector, now is 1D array
> R> y <- matrix(1:4, 1,4) # 1x4 matrix
> R> x + y # Used to return a 1x4 matrix
> Error in x + y : non-conformable arrays
> I agree with the change, but I would beware that some puzzled users may not
> associate new "tapply problems" with this news item.
We are aware of a couple of such problems, but they are code that should
not have worked before. Unfortunately, in S tapply gives a vector and not
a 1D array here ....
> Also, *should* you be able to add a (4) array to a (1,4) array?
No. You cannot in S.
Brian D. Ripley, ripley at 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 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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