This is also mentioned in FAQ 7.31 http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f
Also if you search the R-help archives for 'precision' you can find a lot of threads discussing the issue in further depth. On Sun, Jul 11, 2010 at 9:02 PM, Wu Gong <w...@mtmail.mtsu.edu> wrote: > > I don't know the real reason, but help("==") gives some clues. > > For numerical and complex values, remember == and != do not allow for the > finite representation of fractions, nor for rounding error. Using all.equal > with identical is almost always preferable. See the examples. > > x1 <- 0.5 - 0.3 > x2 <- 0.3 - 0.1 > x1 == x2 # FALSE on most machines > identical(all.equal(x1, x2), TRUE) # TRUE everywhere > > > ----- > A R learner. > -- > View this message in context: > http://r.789695.n4.nabble.com/problem-with-comparisons-for-vectors-tp2285557p2285685.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > 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. > -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ R-help@r-project.org mailing list 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.