Re: [R] Precision in R

From: Marc Schwartz <>
Date: Wed 21 Jul 2004 - 03:50:55 EST

On Tue, 2004-07-20 at 12:13, Duncan Murdoch wrote:
> On Tue, 20 Jul 2004 11:55:32 -0400, 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:
> This isn't relevant to your question, but I found the history of the
> development of the standard interesting:
> Duncan Murdoch


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

More information on Excel's varied compliance with the IEEE 754 standard is available here;en-us;78113

The official IEEE 754 page is at 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 mailing list PLEASE do read the posting guide! Received on Wed Jul 21 03:57:26 2004

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