[R] number point under-flow

[Prof Brian Ripley]

Note R-patched and R-devel get more accurate answers.

On Wed, 4 Feb 2004, Uwe Ligges wrote:

> Roger D. Peng wrote:
> 
> > Did you compile with gcc-2.96?  I think there were some problems with 
> > the floating point arithmetic with that compiler (at least for the 
> > earlier versions released by Red Hat).
> 
> Not (solely) a gcc-2.96 bug, since we get
> 
>    phyper(24, 514, 5961-514, 53, lower.tail=F)
> [1] -3.325784e-12
> 
> on Windows compiled with gcc-3.3.1
> 
> Uwe Ligges
> 
> 
> > -roger
> > 
> > Arne.Muller at aventis.com wrote:
> > 
> >> Hello,
> >>
> >> I've come across the following situation in R-1.8.1 (compile + running 
> >> under
> >> RedHat 7.1):
> >>
> >>
> >>> phyper(24, 514, 5961-514, 53, lower.tail=T)
> >>
> >>
> >> [1] 1
> >>
> >>> phyper(24, 514, 5961-514, 53, lower.tail=F)
> >>
> >>
> >> [1] -1.037310e-11
> >>
> >> I'd expect the later to be 0 or some very small positive number. Is 
> >> this a
> >> number under-flow of the calculation? Do you think I'm safe if I just 
> >> set the
> >> result to 0 in these cases?
> >>
> >>     kind regards,
> >>
> >>     Arne
> >>
> >> ______________________________________________
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> >> http://www.R-project.org/posting-guide.html
> >>
> > 
> > ______________________________________________
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> > https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide! 
> > http://www.R-project.org/posting-guide.html
> 
> ______________________________________________
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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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