On Mon, 19 Jun 2006, Hans-Peter wrote: > Hi, > > I execute the following code snippet.What I don't understand is, that in the > first two cases the numbers shown don't correnspondant to the input (though > I have set the options to show 22 digits). When I assign the third number > which has one place, the display of the numbers is suddenly correct. > > Can anybody explain what happens here?
The problem is that you have set the options to show 22 digits, but the numbers are stored to fewer than 16 digits > .Machine$double.eps [1] 2.220446049250313080847e-16 Everything displayed after the 16th digit is effectively random (the actual values probably depend on exactly when the numbers are loaded into the 80-bit floating point registers on the CPU). The actual results will vary from system to system (on my Linux system the output of x is the same at all stages, and is different from what you report), but nothing beyond the sixteenth digit is at all meaningful. -thomas > (this is just a sample, my real problem lies in numbers that I import from a > datafile and I don't know how to control them when this switching occurs) > > ########################### > options( digits=22 ) > x <- matrix(NA, 3,1) > x[1] <- 6.94788635771657950 > x # 6.947886357716580 # DIFFERENT ??? > # NA > # NA > x[1] == 6.94788635771657950 # but is the same > > x[2] <- 8.34284937565404050 > x # 6.947886357716580 # DIFFERENT ??? > # 8.342849375654041 # DIFFERENT ??? > # NA > x[1] == 6.94788635771657950 # but is the same > > x[3] <- 0.19043842368566377 > x # 6.94788635771657950 # NOW OK!!! > # 8.34284937565404050 # " " > # 0.19043842368566377 # " " > x[1] == 6.94788635771657950 # but is the same > > > ### > platform i386-pc-mingw32 > arch i386 > os mingw32 > system i386, mingw32 > status > major 2 > minor 3.1 > year 2006 > month 06 > day 01 > svn rev 38247 > language R > version.string Version 2.3.1 (2006-06-01) > > > -- > Regards, > Hans-Peter > > [[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 > Thomas Lumley Assoc. Professor, Biostatistics [EMAIL PROTECTED] University of Washington, Seattle ______________________________________________ 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