There is a simple way to get closer to how a floating point number is stored in R with dput():
> dput(min(dataset$gpa)) 1.89999997615814 > dput(dataset$gpa[290]) 1.89999997615814 So you can see, the minimum is not 1.9, just very close to 1.9. ------------------------------------- David L Carlson Department of Anthropology Texas A&M University College Station, TX 77840-4352 -----Original Message----- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Rolf Turner Sent: Tuesday, October 6, 2015 3:53 AM To: Berend Hasselman Cc: r-help@r-project.org; Neverstop Subject: Re: [R] Strange Bug in R On 06/10/15 21:28, Berend Hasselman wrote: > >> On 6 Oct 2015, at 09:24, Neverstop <nevers...@hotmail.it> wrote: >> >> Hi all. >> I don't understand why R works this way: >>> rm(list=ls()) >>> require(foreign) >>> dataset <- read.dta("http://www.ats.ucla.edu/stat/data/ologit.dta";) >>> min(dataset$gpa) >> [1] 1.9 >>> min(dataset$gpa)>=1.90 >> [1] FALSE >>> min(dataset$gpa)>=1.9 >> [1] FALSE >>> min(dataset$gpa)>1.89 >> [1] TRUE >> Shouldn't I get 3 TRUEs? >> Am I missing something? >> Thank you. >> >> > > See R FAQ 7.31 in https://cran.r-project.org/doc/FAQ/R-FAQ.html > It should provide clarification for your puzzlement. Not really. The problem is one of the precision to which a floating point number is *printed* rather than one of the way that floating point numbers are *calculated*. Hence it is not an instance of the counter-intuitive nature of floating point arithmetic. I.e. you could have numbers a and b that were calculated and stored to *infinite* precision, appear to be equal when printed to some default number of significant figures, but are not actually equal. The problems are related and both involve having some understanding of floating point numbers, but they are not the same problem. cheers, Rolf Turner -- Technical Editor ANZJS Department of Statistics University of Auckland Phone: +64-9-373-7599 ext. 88276 ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
