2, 2.0, 2e0 are all double while 2L is an integer. On Fri, May 16, 2008 at 10:56 AM, Erik Iverson <[EMAIL PROTECTED]> wrote: > Dear R-help - > > I have thought about this question for a bit, and come up with no > satisfactory answer. > > Say I have the numeric vector t1, given as > > t1 <- c(1.0, 1.5, 2.0, 2.5, 3.0) > > I simply want to reliably extract the unique integers from t1, i.e., the > vector c(1, 2, 3). This is of course superficially simple to carry out. > > However, my question is related to R FAQ 7.31, "Why doesn't R think these > numbers are equal?" The first sentence of that FAQ reads, "The only numbers > that can be represented exactly in R's numeric type are integers and > fractions whose denominator is a power of 2." > > All the methods I've devised to do the above task seem to ultimately rely on > the fact that identical(x.0, x) == TRUE, for integer x. > > My assumption, which I'm hoping can be verified, is that, for example, 2.0 > (when, say, entered at the prompt and not computed from an algorithm) is an > integer in the sense of FAQ 7.31. > > This seems to be the case on my machine. > >> identical(2.0, 2) > [1] TRUE > > Apologies that this is such a trivial question, it seems so obvious on the > surface, I just want to be sure I am understanding it correctly. > > Erik Iverson > [EMAIL PROTECTED] > > sessionInfo() > R version 2.7.0 (2008-04-22) > i686-pc-linux-gnu > > locale: > LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C > > attached base packages: > [1] grDevices datasets tcltk splines graphics utils stats > [8] methods base > > other attached packages: > [1] fortunes_1.3-4 debug_1.1.0 mvbutils_1.1.1 SPLOTS_1.3-47 > [5] Hmisc_3.4-3 chron_2.3-21 survival_2.34-1 erik_0.0-1 > > loaded via a namespace (and not attached): > [1] cluster_1.11.10 grid_2.7.0 lattice_0.17-6 > > ______________________________________________ > 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. >
______________________________________________ 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.