[Rd] min/max of a vector with NAs and NaNs

[Prof Brian Ripley]

On Wed, 23 Feb 2011, Hervé Pagès wrote:

> I get this (with R-2.12 and R-2.13, didn't try with earlier versions):
>
>> max(c(NaN, NA))
> [1] NA
>> max(c(NA, NaN))
> [1] NaN
>
> I get the same thing with min().
>
> The fact that the result of 'max(x)' or 'min(x)' depends on the order
> of the elements in 'x' is surprising. It also seems to contradict the
> man page:
>
>     By definition the min/max of a numeric vector containing an ‘NaN’
>     is ‘NaN’, except that the min/max of any vector containing an ‘NA’
>     is ‘NA’ even if it also contains an ‘NaN’.

This seemed to depend on the compiler, and in your case the compiler 
has optimized away the code to achieve this.   I've changed the code 
in R-devel to something that seems to be more robust.  Note that the 
comment did not apply to max(NA, NaN), but that should also now be 
consistent.

>
> Cheers,
> H.
>
> -- 
> Hervé Pagès
>
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M2-B876
> P.O. Box 19024
> Seattle, WA 98109-1024
>
> E-mail: hpages at fhcrc.org
> Phone:  (206) 667-5791
> Fax:    (206) 667-1319
>
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>

-- 
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)
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