There is no bug, of course, this is a common floating point arithmetic misunderstanding.
> print(2.01, digits = 20) [1] 2.0099999999999997868 Please search for "What every scientist should know about floating-point arithmetic" and you'll hopefully understand what the "bug" is. Hth, Adrian On Sat, Feb 18, 2017 at 6:18 AM, T. Zhang <t...@me.com> wrote: > Hello, > > Today I happened to notice a strange error in R. If you type > (2.01-0.06)==1.95, output from R is “FALSE”, which is wrong. But if you > type (1.01-0.06)==0.95, output is “TRUE”, which is correct. I tested this > in two systems: R 3.3.2 in my iMac and R 3.2.0 on my school’s Linux server. > Both gave same outputs. As shown in the following: > > > 2.01-0.06 > [1] 1.95 > > (2.01-0.06)==1.95 # should be TRUE; output is wrong > [1] FALSE > > 1.01-0.06 > [1] 0.95 > > (1.01-0.06)==0.95 # should be TRUE; output is correct > [1] TRUE > > (2.01-0.06)>1.95 # should be FALSE; output is correct > [1] FALSE > > (2.01-0.06)<1.95 # should be FALSE; output is wrong > [1] TRUE > > Similar errors could be found with simple alterations of the above inputs, > such as: > > 5.533-5.412 > [1] 0.121 > > (5.533-5.412)==0.121 # should be TRUE; output is wrong > [1] FALSE > > 2.533-2.412 > [1] 0.121 > > (2.533-2.412)==0.121 # should be TRUE; output is correct > [1] TRUE > > Could any of you test whether you have same outputs as mine? And does > anyone know what is wrong with these? My guess is that R has a bug in > processing double numbers. Thanks! > > TZ > ______________________________________________ > 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. -- Adrian Dusa University of Bucharest Romanian Social Data Archive Soseaua Panduri nr. 90-92 050663 Bucharest sector 5 Romania [[alternative HTML version deleted]] ______________________________________________ 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.
