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RE: st: RE: RE: highest scalar of a matrix


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: RE: highest scalar of a matrix
Date   Fri, 6 Jun 2003 18:45:41 +0100

David Kantor

> > > > I'm looking for a function or a routine in Stata7 which would
> > > > give me the
> > > > highest scalar of a matrix
> 
> Both Nick Winter & Nick Cox replied.
> 
> I would just add a warning.  In Nick Winter's program,
> 
>  >       if `M'[`r',`c']>`val' {
>  >         scalar `val'=`M'[`r',`c']
> 
> will pick up missing values if any are present in `M', 
> which is possible in 
> Stata 8 (even if your program
> states version 7).
> 
> Unless you want to count a missing as a maximal value, that 
> condition should be
>    if ~mi(`M'[`r',`c']) & (`M'[`r',`c'] > `val  | mi(`val') ) {
> 
> Why did I throw in that condition mi(`val') ?  Because 
> `val' is pre-loaded 
> with `M'[1,1], so it, too, may be missing, until it is 
> replaced when the 
> first nonmissing value is encountered.
> 
> (Now, given this more robust test, you could pre-load `val' 
> with missing, 
> rather than `M'[1,1].)
> 
> I am not familiar with the -matmax- program by Jeroen 
> Weesie, so I don't 
> know whether it takes this approach.

The original desire was clearly stated 
as code for Stata 7, and I believe that both 
Nick Winter's code and Jeroen's Weesie's, which 
can be downloaded from his website, are fine 
for that question. 

As for Stata 8, David has a good point. 

A little more can be said. 

Jeroen's code also initialises with the [1,1] 
element; it doesn't work if that is missing, 
but that is a matter of version control (see 
-help version-.) 

Jeroen's code is not, I think, broken by missing elements 
in any other position, and this is because it 
works with this rule 

maximum so far = max(this element, maximum so far) 

and -max()- only returns missing if all its arguments 
are missing. 

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

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