From ?NA
Numerical computations using ‘NA’ will normally result in ‘NA’: a
possible exception is where ‘NaN’ is also involved, in which case
either might result.
and ?NaN
Computations involving ‘NaN’ will return ‘NaN’ or perhaps ‘NA’:
which of those two is not guaranteed and may depend on the R
platform (since compilers may re-order computations).
fortunes::fortune(14) applies (yet again).
On 01/04/2017 04:50, Henrik Bengtsson wrote:
In R 3.3.3, I observe the following on Ubuntu 16.04 (when building
from source as well as for the sudo apt r-base build):
x <- c(NA, NaN)
mean(x)
[1] NA
mean(rev(x))
[1] NaN
rowMeans(matrix(x, nrow = 1, ncol = 2))
[1] NA
rowMeans(matrix(rev(x), nrow = 1, ncol = 2))
[1] NaN
.rowMeans(x, m = 1, n = 2)
[1] NA
.rowMeans(rev(x), m = 1, n = 2)
[1] NaN
.rowSums(x, m = 1, n = 2)
[1] NA
.rowSums(rev(x), m = 1, n = 2)
[1] NaN
rowSums(matrix(x, nrow = 1, ncol = 2))
[1] NA
rowSums(matrix(rev(x), nrow = 1, ncol = 2))
[1] NaN
I'd expect NA to trump NaN in all cases (with na.rm = FALSE). sum()
does not have this problem and returns NA in both cases (*).
For the same R version build from source on RHEL 6.6 system
(completely different architecture), I get the expected result (= NA)
for all of the above cases, e.g.
x <- c(NA, NaN)
mean(x)
[1] NA
mean(rev(x))
[1] NA
[...]
Before going insane trying to troubleshoot this, I have a vague memory
that this, or something related to this, has been discussed
previously, but I cannot locate it.
Is the above a bug in R, a FAQ, a build error, overzealous compiler
optimization, and / or ...?
Thanks,
Henrik
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
