> On Wednesday, May 20, 2020, 7:00:09 AM EDT, peter dalgaard > <pda...@gmail.com> wrote: > > Expected, see FAQ 7.31. > > You just can't trust == on FP operations. Notice also
Additionally, since you're implementing a "mean" function you are testing against R's mean, you might want to consider that R uses a two-pass calculation[1] to reduce floating point precision error. Best, Brodie. [1] https://github.com/wch/r-source/blob/tags/R-4-0-0/src/main/summary.c#L482 > > a2=(z[idx]+x[idx]+y[idx])/3 > > a2==a > [1] FALSE > > a2==b > [1] TRUE > > -pd > > > On 20 May 2020, at 12:40 , Morgan Morgan <morgan.email...@gmail.com> wrote: > > > > Hello R-dev, > > > > Yesterday, while I was testing the newly implemented function pmean in > > package kit, I noticed a mismatch in the output of the below R expressions. > > > > set.seed(123) > > n=1e3L > > idx=5 > > x=rnorm(n) > > y=rnorm(n) > > z=rnorm(n) > > a=(x[idx]+y[idx]+z[idx])/3 > > b=mean(c(x[idx],y[idx],z[idx])) > > a==b > > # [1] FALSE > > > > For idx= 1, 2, 3, 4 the last line is equal to TRUE. For 5, 6 and many > > others the difference is small but still. > > Is that expected or is it a bug? ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
