[Rd] bug? (PR#8074)

Paul Mosquin pmosquin at hotmail.com
Wed Aug 17 03:33:13 CEST 2005


Thank you for your response.  I checked the FAQ and it provides an example 
using sqrt(2) where you'd expect numerical precision to be an issue.

I guess that I expect R to act pretty much as C or C++ would do if I were to 
program the same code.  It's a bit of a surprise that assignment of 
rationals, well within precision, followed by multiplication leading to a 
result well within precision picks up those extra bits along the way.  
Something to watch out for, to be sure.

Thanks again for your help


>From: Thomas Lumley <tlumley at u.washington.edu>
>To: pmosquin at hotmail.com
>CC: r-devel at stat.math.ethz.ch, R-bugs at biostat.ku.dk
>Subject: Re: [Rd] bug? (PR#8074)
>Date: Tue, 16 Aug 2005 16:06:48 -0700 (PDT)
>On Wed, 17 Aug 2005 pmosquin at hotmail.com wrote:
>>I just don't understand this:
>>[1] TRUE
>>[1] 0.04
>>[1] FALSE
>It's a FAQ, not a bug. Consider:
>>(.2*.2) - .04
>[1] 6.938894e-18
>and read the FAQ
>	-thomas
>>[1] 0.04
>>[1] 0.04
>>[1] FALSE
>>R-devel at r-project.org mailing list
>Thomas Lumley			Assoc. Professor, Biostatistics
>tlumley at u.washington.edu	University of Washington, Seattle

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