On 7 Sep 2004, Peter Dalgaard wrote: > Robin Hankin <[EMAIL PROTECTED]> writes: > > > Dear Professor Ripley > > > > thank you for your reply. > > > > > > > >> > NaN +NA > > >> [1] NaN > > >> > NA + NaN > > >> [1] NA > > >> > > >> I thought "+" was commutative by definition. What's going on? > > > > > >It is clearly not under your compiler/OS. We could add a configure test > > >for broken systems and fix it in arithmetic.c but it hardly seems > > >worthwhile. > > Didn't we do this discussion before?
Certainly over NA vs 0+NA, as in this excerpt from reg-tests-1.R ## matching NAs on Solaris (MM 2002-08-02) # x <- as.double(NA) # identical(x + 0, x) # stopifnot(match(x + 0, x, 0) == 1) ## match failed on Solaris with some compiler settings ## NA+0 is not guaranteed to be NA: could be NaN > AFAIR, the thing is that IEEE > specifies that NaN + whatever == whatever + NaN == NaN, but NaN is > only specified a bit pattern in the first couple of bytes. R uses a > special value in the lower bytes (1954 -- BTW, when *is* Ross' > birthday?) to signal the NA, but we can't really expect that chip > makers do what we hope they'd do with that part of the value. I think > we resolved that specific checking for this issue would be too much of > a performance killer, especially since R generally treats NaN as NA > anyway. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
