Please do note that this too is a reading error. The documentation for
rowsum() says
group: a vector giving the grouping, with one element per row of
'x'.
R has used 'group' as if it were as.vector(group), as it was entitled to
do. If you do not want that, give a _vector_ with the property you do
want, e.g. as.character(group).
You could also call rowsum() with reorder=FALSE and reorder later to your
taste.
On Thu, 17 Aug 2006, Brahm, David wrote:
> On 8/3/2006 10:34 AM, <[EMAIL PROTECTED]> noted that,
> starting with R-2.3.0, sort() fails to preserve date classes:
>
> > dates <- seq(Sys.Date(), len=5, by="1 day")
> > dates[order(dates)]
> > [1] "2006-08-03" "2006-08-04" "2006-08-05" "2006-08-06" "2006-08-07"
> > sort(dates)
> > [1] 13363 13364 13365 13366 13367
>
> and Duncan Murdoch <[EMAIL PROTECTED]> replied:
>
> > The problem is that some classes assume a particular ordering for
> > values; sort can mess them up. If you know that's not the case, you
> > can protect the class yourself:
> > cl <- class(dates)
> > sorteddates <- sort(dates)
> > class(sorteddates) <- cl
>
> I have to agree with Stephen (and Alex Dannenberg in another post)
> that this change is unfortunate for date classes. How do you
> reproduce this old behavior (without assuming alphanumeric ordering):
>
> > x <- matrix(1:12, 4,3)
> > group <- Sys.Date() + c(0,1,0,1)
> > rowsum(x, group)
> [,1] [,2] [,3]
> 2006-08-17 4 12 20
> 2006-08-18 6 14 22
>
> Under R-2.3.1, the result is now:
> [,1] [,2] [,3]
> 13377 4 12 20
> 13378 6 14 22
>
> Blech!
>
> -- David Brahm ([EMAIL PROTECTED])
--
Brian D. Ripley, [EMAIL PROTECTED]
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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