From: Liaw, Andy <andy_liaw_at_merck.com>

Date: Wed 21 Jul 2004 - 03:01:13 EST

R-help@stat.math.ethz.ch 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 Received on Wed Jul 21 03:10:16 2004

Date: Wed 21 Jul 2004 - 03:01:13 EST

You can find the info in ?numeric, which says:

Note:

_R has no single precision data type. All real numbers are stored in double precision format_. ...

I suspect the most likely difference is in the actual algorithms used for the least squares computation. AFAIK SAS uses the sweep operator on the extended cross-product matrix, whereas lm() in R uses QR decomposition on the X matrix.

You can read Prof. Bates' article on least squares computations in R in the most recent issue of the R News, available on www.r-project.org.

**HTH,
**

Andy

*> From: adelmaas@musc.edu
**>
*

> Greetings.

*>
**> I'm trying to recreate in R some regression models I've done in SAS,
**> but I'm not getting the same results. My advisor suspects
**> this may be
**> due to differences in precision between R and SAS. Does anyone know
**> where I can find specifications for R's type double? (It
**> doesn't seem
**> to be in the R Language Definition.) Thanks in advance for any help
**> anyone can provide.
**>
**> Aaron
**>
**> -------------
**> Aaron Solomon (ben Saul Joseph) Adelman
**> E-mail: adelmaas@musc.edu
**> Web site: http://people.musc.edu/~adelmaas/
**> AOL Instant Messenger & Yahoo! Messenger: Hiergargo
**> AIM chat-room (preferred): Adelmania
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch 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
**>
**>
*

R-help@stat.math.ethz.ch 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 Received on Wed Jul 21 03:10:16 2004

*
This archive was generated by hypermail 2.1.8
: Wed 03 Nov 2004 - 22:55:07 EST
*