On 28-Aug-11 03:59:51, edwar...@psu.ac.th wrote: > Dear all, > I am happy to accept that > >> is.integer(1) > [1] FALSE > > But I'm having difficulty with this one: > >> as.integer((2.53-2)*100) > [1] 52 > > especially since: > >> as.integer((1.53-1)*100) > [1] 53 > > Although I know that this is a precision issue since > >> x <- (2.53-2)*100 >> x-53 > [1] -2.131628e-14 > > And I can always use the round function to get what I want, > but I just wonder if something is wrong here. > >> sessionInfo() > R version 2.13.1 (2011-07-08) > Platform: i386-pc-mingw32/i386 (32-bit) > > locale: > [1] LC_COLLATE=Thai_Thailand.874 LC_CTYPE=Thai_Thailand.874 > LC_MONETARY=Thai_Thailand.874 > [4] LC_NUMERIC=C LC_TIME=Thai_Thailand.874 > > attached base packages: > [1] stats graphics grDevices utils datasets methods base > > Thanks, > Edward
It depends on what you mean by "wrong"! Perhaps "unexpected" might be better! The key to the matter is described in '?as.integer' under "Value": Non-integral numeric values are truncated towards zero (i.e., ?as.integer(x)? equals ?trunc(x)? there) ... so that as.integer(2) # [1] 2 as.integer(2 + 2e-14) # [1] 2 as.integer(2 - 2e-14) # [1] 1 as.integer(-2 + 2e-14) # [1] -1 as.integer(-2 - 2e-14) # [1] -2 so it is doing "what it says on the box". Yes, you are better using round()! Hoping this helps to clear it up, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Fax-to-email: +44 (0)870 094 0861 Date: 28-Aug-11 Time: 09:24:14 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
