[R] Inefficiency of SAS Programming

Fri Feb 27 15:18:47 CET 2009

Yes Frank, I accept your point but nevertheless IML is the proper place for
matrix work in SAS - mixing macro-level logic and computation is another
question - R is certainly more seemless in this respect.

Gerard

             Frank E Harrell                                               
             Jr                                                            
             <f.harrell at vander                                          To 
             bilt.edu>                 "Gerard M. Keogh"                   
                                       <GMKeogh at justice.ie>                
             27/02/2009 13:55                                           cc 
                                       R list <r-help at stat.math.ethz.ch>,  
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                                                                   Subject 
                                       Re: [R] Inefficiency of SAS         
                                       Programming                         

Gerard M. Keogh wrote:
> Frank,
>
> I can't see the code you mention - Web marshall at work - but I don't
think
> you should be too quick to run down SAS - it's a powerful and flexible
> language but unfortunately very expensive.
>
> Your example mentions doing a vector product in the macro language - this
> only suggest to me that those people writing the code need a crash course
> in SAS/IML (the matrix language). SAS is designed to work on records and
so
> is inapproprorriate for matrices - macros are only an efficient code
> copying device. Doing matrix computations in this way is pretty mad and
the
> code would be impossible never mind the memory problems.
> SAS recognise that but a lot of SAS users remain familiar with IML.
>
> In IML by contrast there are inner, cross and outer products and a raft
of
> other useful methods for matrix work that R users would be familiar with.
> OLS for example is one line:
>
> b = solve(X`X, X`y) ;
> rss = sqrt(ssq(y - Xb)) ;
>
> And to give you a flavour of IML's capabilities I implemented a SAS
version
> of the MARS program in it about 6 or 7 years ago.
> BTW SPSS also has a matrix language.
>
> Gerard

But try this:

PROC IML;
... some custom user code ...
... loop over j=1 to 10 ...
...   PROC GENMOD, output results back to IML
...

IML is only a partial solution since it is not integrated with the PROC
step.

Frank

>
>
>
>

>              Frank E Harrell

>              Jr

>              <f.harrell at vander
To
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>                                        [R] Inefficiency of SAS
Programming
>

>              26/02/2009 22:57

>

>

>

>

>
>
>
>
> If anyone wants to see a prime example of how inefficient it is to
> program in SAS, take a look at the SAS programs provided by the US
> Agency for Healthcare Research and Quality for risk adjusting and
> reporting for hospital outcomes at
> http://www.qualityindicators.ahrq.gov/software.htm .  The PSSASP3.SAS
> program is a prime example.  Look at how you do a vector product in the
> SAS macro language to evaluate predictions from a logistic regression
> model.  I estimate that using R would easily cut the programming time of
> this set of programs by a factor of 4.
>
> Frank
> --
> Frank E Harrell Jr   Professor and Chair           School of Medicine
>                       Department of Biostatistics   Vanderbilt University
>
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--
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University