On Mon, Jun 18, 2012 at 12:58:13PM -0700, hamoreno wrote: > Hi all, > > Is there any problem of precision when using seq?. For example: > > x<- seq(0,4,0.1) > x[4]=0.3 > > BUT: > > x[4]-0.3=5.551115e-17 > > It means when I use this condition within an if clause, it does not find > values with 0.3 for x[4] as it is not precisely 0.3.
Hi. Using round() is reasonably secure. x <- round(seq(0,4,0.1), digits=7) x[4] == 0.3 [1] TRUE None of the compared nunbers is 0.3, but they are both rounded to the closest representable number to 0.3. print(x[4], digits=20) [1] 0.2999999999999999889 print(0.3, digits=20) [1] 0.2999999999999999889 See also http://rwiki.sciviews.org/doku.php?id=misc:r_accuracy for some more hints related to this. Petr Savicky. ______________________________________________ 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.
