On 3/12/2006 7:08 PM, Janusz Kawczak wrote: > However, mean(x)==0.2 returns TRUE > Also, mean(x)>=(1-0.8) returns TRUE ;) > > So, it's not just the approximation calculus.
I don't get your point. On my computer, > 1-0.8 < 0.2 [1] TRUE which is consistent with what I wrote below and what you write above. mean(x) comes out to the same approximation as the constant 0.2 uses, but 1-0.8 doesn't, it comes out smaller. Duncan Murdoch > > On Sun, 12 Mar 2006, Duncan Murdoch wrote: > >> On 3/12/2006 6:39 PM, [EMAIL PROTECTED] wrote: >>> Full_Name: Matthew Davis >>> Version: 2.2.0 >>> OS: OS X (10.4.5) >>> Submission from: (NULL) (209.107.120.195) >>> >>> >>> the mean of my sample x is 0.2, and when I check mean(x)<=0.2 I get a TRUE >>> value, when I check mean(x)<=(1-0.8) I get a FALSE value. (x <- c(0, 1, 0, >>> 0, >>> 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0)) >> Why make this so complicated? The natural conclusion from that is that >> 0.2 is not equal to (1-0.8), and indeed: >> >> > (1-0.8) == 0.2 >> [1] FALSE >> >> The problem is that neither 0.2 nor 0.8 can be represented exactly, so >> when you do calculations using them you are doing approximations. The >> approximation involving your mean is different than the one involving >> (1-0.8). This is an FAQ, >> >> 7.31 Why doesn't R think these numbers are equal? >> >> This is not a bug. >> >> Duncan Murdoch >> >> ______________________________________________ >> R-devel@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
