I must admit I had never realised this so thanks to Monica for raising it.
Round-to-even is used for statistical reasons and there is some point as it obviously reduces bias. But why should the decision be to round to the nearest even number? rounding to the nearest odd number would be equally valid. (signif(x,0) is the same as round(). ) There is a debate and sometimes you need symmetric rounding. Perhaps there should be an option in round that defaults to round-to-even for compatibility but includes the various other rounding approaches as seen for example in http://en.wikipedia.org/wiki/Rounding BTW with Fortran the 'nearest integer' approach is used: REAL*8 TEST 10 CONTINUE READ(*,*)TEST WRITE(*,*)TEST,IDNINT(TEST) GOTO 10 END Compiling this under g77 and gfortran gives the result: ~ $ g77 idnint.f -o idnint ~ $ ./idnint 1.5 1.5 2 2.5 2.5 3 ~ $ gfortran idnint.f -o idnint ~ $ ./idnint 2.5 2.50000000000000 3 1.5 1.50000000000000 2 Octave: octave:1> round(1.5) ans = 2 octave:2> round(2.5) ans = 3 On Thursday 02 August 2007 21:46:36 Monica Pisica wrote: > Hi again, > > Mea culpa for not reading help pages before hand - but one would not go > there when the function syntax is obvious and known .... besides other > programming languages (for example IDL) with same function do not round to > the next even number .... so i do get 3 for round(2.5), and i didn't > realize that it is "normal" for R to give a 2 instead of 3.> Date: Thu, 2 > Aug 2007 22:38:49 +0200> From: [EMAIL PROTECTED]> To: > [EMAIL PROTECTED]> CC: r-help@stat.math.ethz.ch> Subject: Re: [R] - > round() strange behaviour> > On Thu, 2 Aug 2007, Monica Pisica wrote:> > >> > > Hi,> >> > I am getting some strange results using round - it seems that > it depends if the number before the decimal point is odd or even ....> >> > > For example:> >> > > round(1.5)[1] 2> round(2.5)[1] 2> > While i would > expect that round(2.5) be 3 and not 2.> >> > Do you have any explanation > for that?> > Yes: you obviously did not read the man page! Please do.> Z> > > > I really appreciate your input,> >> > Monica> >> >> > > _________________________________________________________________> > > [[trailing spam removed]]> >> > [[alternative HTML version deleted]]> >> > > ______________________________________________> > R-help@stat.math.ethz.ch > 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.> >> >> > _________________________________________________________________ > Messenger Caf� � open for fun 24/7. Hot games, cool activities served > daily. Visit now. > > [[alternative HTML version deleted]] -- Best wishes John John Logsdon "Try to make things as simple Quantex Research Ltd, Manchester UK as possible but not simpler" [EMAIL PROTECTED] [EMAIL PROTECTED] +44(0)161 445 4951/G:+44(0)7717758675 www.quantex-research.com
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