On Tue, 2004-07-20 at 12:13, Duncan Murdoch wrote: > On Tue, 20 Jul 2004 11:55:32 -0400, [EMAIL PROTECTED] wrote : > >Does anyone know > >where I can find specifications for R's type double? > > As far as I know, all platforms use the IEEE-754 standard double > precision numbers. Google will give you a description; here's one: > > http://research.microsoft.com/~hollasch/cgindex/coding/ieeefloat.html > > This isn't relevant to your question, but I found the history of the > development of the standard interesting: > > http://http.cs.berkeley.edu/~wkahan/ieee754status/754story.html > > Duncan Murdoch
Duncan, The standard is there, but not all applications stick to it faithfully. A good example being how certain <cough> spreadsheets <\cough> deal with numbers "close to zero". For example, Excel will round numbers "close to zero" to zero. You may recall this thread from last year covered this topic http://maths.newcastle.edu.au/~rking/R/help/03a/6597.html More information on Excel's varied compliance with the IEEE 754 standard is available here http://support.microsoft.com/default.aspx?scid=kb;en-us;78113 The official IEEE 754 page is at http://grouper.ieee.org/groups/754/ and there are some good reading materials and FAQ's there. This above is beyond the scope of SAS in particular, but I suspect that the difference that Aaron is experiencing, as Andy has noted, is methodologic and not precision related. Aaron, one other source for information on the precision of R on your particular machine is the use of .Machine, which will provide you with a list of specifications. See ?.Machine for additional information here. HTH, Marc Schwartz ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html