[R] That dreaded floating point trap

[ONKELINX, Thierry]

Dear Alexander,

Instead of testing 'somevector > 0.4', test 'abs(somevector - 0.4) < some.small.number'

Best regards,

Thierry

----------------------------------------------------------------------------
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium

Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
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Belgium

tel. + 32 54/436 185
Thierry.Onkelinx op inbo.be
www.inbo.be

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> -----Oorspronkelijk bericht-----
> Van: r-help-bounces op r-project.org 
> [mailto:r-help-bounces op r-project.org] Namens Alexander Engelhardt
> Verzonden: donderdag 31 maart 2011 14:57
> Aan: r-help op r-project.org
> Onderwerp: Re: [R] That dreaded floating point trap
> 
> Am 31.03.2011 14:41, schrieb Sarah Goslee:
> > On Thu, Mar 31, 2011 at 8:14 AM, Alexander Engelhardt
> >> this helps, thank you.
> >> But if this code is in a function, and some user supplies 
> a vector, I 
> >> will still have to round it in the function, I guess.
> >>
> >> It's weird how 0.1 is different from round(0.1, digits=1) , but I 
> >> don't want to read that 90 page long floating point paper 
> which was 
> >> referenced somewhere :)
> >
> >
> > Or you could try the much shorter R FAQ 7.31. Turns out it 
> isn't weird 
> > at all, if you are a computer.
> 
> You're a computer! :)
> 
> But yes.. the FAQ entry was where I found all.equal and the 
> referenced 90-page-paper. But I didn't find out how to do a 
> subset with 'somevector  > 0.4'.
> 
> I think I'll have to round the numbers every time now.. or 
> use some other not-so-pretty workaround like 'somevector > 
> 0.4 - 0.05' for 0.1-binned data.
> 
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