'normalized' is key. A normalized double precision floating point number has 52 binary digits of precision and .Machine$double.eps/2 does not. E.g.,
> bitsOfPrecision <- function(x)max(which( x != x*(1+2^-(1:60)))) > bitsOfPrecision(4) [1] 52 > bitsOfPrecision(.Machine$double.xmin) [1] 52 > bitsOfPrecision(.Machine$double.xmin/2) [1] 51 > bitsOfPrecision(.Machine$double.xmin/4) [1] 50 Google for 'normalized floating point'. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of Marius Hofert > Sent: Tuesday, September 10, 2013 2:50 PM > To: R-help > Subject: [R] double.xmin really the smallest non-zero normalized > floating-point number? > > Hi, > > ?.Machine says that 'double.xmin' is 'the smallest non-zero normalized > floating-point number'. On my machine, this is 2.225074e-308. However, > 2.225074e-308 / 2 is > 0 and smaller than 2.225074e-308, so > double.xmin is not the smallest such number (?) Am I missing anything? > > Cheers, > > Marius > > ______________________________________________ > [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 > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ [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 and provide commented, minimal, self-contained, reproducible code.
