Hi, I obtain the same result under Win. XP SP2 on AMD 64 3700+
platform i386-pc-mingw32 arch i386 os mingw32 system i386, mingw32 status major 2 minor 2.0 year 2005 month 10 day 06 svn rev 35749 language R > m <- matrix(c(1,0,7,15),2,2) ; chisq.test(m, sim=TRUE)$p.value [1] 0.3598201 > m <- matrix(c(1,0,7,16),2,2) ; chisq.test(m, sim=TRUE)$p.value [1] 0.0004997501 > m <- matrix(c(1,0,7,17),2,2) ; chisq.test(m, sim=TRUE)$p.value [1] 0.3403298 Ciao Simone On 10/20/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > Hi, > > This report deals with p-values coming from chisq.test using > the simulate.p=TRUE option. The issue is numerical accuracy > and was brought up in previous bug reports 3486 and 3896. > The bug was considered fixed but apparently was only mostly > fixed. Just the typical problem of two values that are > mathematically equal not ending up numerically equivalent. > > Consider this series of three 2x2 tables: > > [1,] 1 7 > [2,] 0 15 > > [1,] 1 7 > [2,] 0 16 > > [1,] 1 7 > [2,] 0 17 > > > The pvals returned from chisq.test(m, sim=TRUE)$p.value are > 0.3543228, 0.0004997501 and 0.3273363 respectively. > > The 2nd seems a bit unlikely, huh? > > I checked into it and the value I'm getting for the statistic > (calculated in R code) is 4*.Machine$double.eps less than the > value (which should be equal) that is returned from the C-code > that does the simulation. > > > Code for creating/testing the three matrices shown above: > m <- matrix(c(1,0,7,15),2,2) ; chisq.test(m, sim=TRUE)$p.value > m <- matrix(c(1,0,7,16),2,2) ; chisq.test(m, sim=TRUE)$p.value > m <- matrix(c(1,0,7,17),2,2) ; chisq.test(m, sim=TRUE)$p.value > > > Running SuSE9.3 on a AMD Athlon4000+ > > > > version > platform i686-pc-linux-gnu > arch i686 > os linux-gnu > system i686, linux-gnu > status Patched > major 2 > minor 1.1 > year 2005 > month 07 > day 29 > language R > > > Thanks, > Doug > > > Douglas Grove > Statistical Research Associate > Fred Hutchinson Cancer Research Center > Seattle WA 98109 > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- ______________________________________________________ Simone Giannerini Dipartimento di Scienze Statistiche "Paolo Fortunati" Universita' di Bologna Via delle belle arti 41 - 40126 Bologna, ITALY Tel: +39 051 2098248 Fax: +39 051 232153 E-mail: [EMAIL PROTECTED] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
