[R] Comparison of SAS & R/Splus
Frank E Harrell Jr
feh3k at spamcop.net
Thu Sep 4 15:34:26 CEST 2003
On Thu, 04 Sep 2003 14:50:25 -0400
"Paul, David A" <paulda at BATTELLE.ORG> wrote:
> I am one of only 5 or 6 people in my organization making the
> effort to include R/Splus as an analysis tool in everyday work -
> the rest of my colleagues use SAS exclusively.
> Today, one of them made the assertion that he believes the
> numerical algorithms in SAS are superior to those in Splus
> and R -- ie, optimization routines are faster in SAS, the SAS
> Institute has teams of excellent numerical analysts that
> ensure its superiority to anything freely available, PROC
> NLMIXED is more flexible than nlme( ) in the sense that it
> allows a much wider array of error structures than can be used
> in R/Splus, &etc.
> I obviously do not subscribe to these views and would like
> to refute them, but I am not a numerical analyst and am still
> a novice at R/Splus. Do there exist refereed papers comparing the
> numerical capabilities of these platforms? If not, are there
> other resources I might look up and pass along to my colleagues?
> Much thanks in advance,
> david paul
I don't have papers comparing the numerical capabilities but I say bunk to your colleagues. The last time I looked, SAS still relies on the out of date Gauss-Jordan sweep operator in many key places, in place of the QR decomposition that R and S-Plus use in regression. And SAS being closed source makes it impossible to see how it really does calculations in some cases.
See http://hesweb1.med.virginia.edu/biostat/s/doc/splus.pdf Section 1.6 for a comparison of S and SAS (though this doesn't address numerical reliability). Overall, SAS is about 11 years behind R and S-Plus in statistical capabilities (last year it was about 10 years behind) in my estimation.
SAS User, 1969-1991
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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