On Fri, 25 Mar 2011, William Dunlap wrote:
(a) In R 2.12.2 rowsum can overflow if given an integer input:
> rowsum(c(2e9L, 2e9L), c("a", "a"))
[,1]
a -294967296
> 2^32 + .Last.value
[,1]
a 4e+09
Should it be changed to coerce its x argument to numeric
(double precision) so it always returns a numeric output?
No, I don't think so. But it should return NA on overflow (as sum()
does), and I've altered pre-2.13.0 to do so.
(b) When rowsum is given an x containing both NaN and NA it
appears to use the last of the NaN/NA entries to determine
if the output is NaN or NA while the `+` function uses the
first:
> z <- cbind( c(NA,NA), c(NA,NaN), c(NaN,NA), c(NaN,NaN))
> rowsum(z, c("a","a"))
[,1] [,2] [,3] [,4]
a NA NaN NA NaN
> z[1,,drop=FALSE] + z[2,,drop=FALSE]
[,1] [,2] [,3] [,4]
[1,] NA NA NaN NaN
Which is not a bug: R does not claim to be consistent about this
(except for a few documented functions), and there are lots of
instances of this.
(The name rowsum is a metabug, since it may be confused
with the entirely different rowSums, but it has been around
for a long time.)
A lot longer than rowSums ...
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
--
Brian D. Ripley, rip...@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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