On Wed, Sep 30, 2009 at 2:32 PM, Peter Dalgaard<p.dalga...@biostat.ku.dk> wrote: > Martin Batholdy wrote: >> >> hum, >> >> can you explain that a little more detailed? >> Perhaps I miss the background knowledge - but it seems just absurd to me. >> >> 0.1+0.1+0.1 is 0.3 - there is no rounding involved, is there? >> >> why is >> x <- 0.1 + 0.1 +0.1 >> not equal to >> y <- 0.3 > > Remember that this is in BINARY arithmetic. It's really not any stranger > than the fact that 1/3 + 1/3 != 2/3 in finite accuracy decimal arithmetic > (0.33333 + 0.33333 = 0.66666 != 0.66667).
In an earlier thread on this theme I believe that someone quoted Brian Kernighan as saying "10 times 0.1 is hardly ever 1" but I haven't been able to track down the quote. Can anyone point us to such a quote? It summarizes the situation succinctly, ______________________________________________ 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.