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st: RE: Mata question: "matrix languages evaluate matrix expressions"?


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Mata question: "matrix languages evaluate matrix expressions"?
Date   Tue, 12 Apr 2005 19:06:59 +0100

My (somewhat informed) guess is that this is 
absolutely nothing to do with a disclaimer 
about lack of precision. There would be no 
point in publishing Mata if it led to 
compromises over precision. 

More generally, as said earlier, I really 
don't think you are going to get good answers 
about such questions for the next two weeks 
or so. StataCorp technical people are just way too busy. 
It would be nice to be wrong on that, but 
I doubt it. 

Nick 
n.j.cox@durham.ac.uk 

Renzo Comolli
 
> At the page
> http://www.stata.com/stata9/mata.html
> it says "Everybody knows that matrix languages evaluate 
> matrix expressions,
> such as b=invsym(X'X)*X'y, and Mata is no exception. Because of Mata's
> design, however, it is fast enough to work at the element level".
> 
> This looks like a disclaimer of some sort about some loss of 
> precision, but
> I got quite understand the implications of this.
> Can anybody clarify?
> 
> How different is it (if any) from the way the same 
> calculation was done in Stata8?

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