st: Mata problem with nonreals [was: Re: Mata finds nonreal although I can't find a no nonreal]

[Dirk Enzmann <dirk.enzmann@uni-hamburg.de>]

The title of my first mail had an error and was misleading: It should 
have been
"Mata rinds nonreal although I can't find a nonreal", even better:
"Why does Mata report nonreals?"

I still have no answer to my question but found a way to get rid of the 
complaint about nonreals: When inserting next to the command line that 
computes A1 via
A1 = S1*(V1:/sqrt(eigv1))*V1'

the command line

A1 = sign(P1):*abs(A1)

Mata does no longer complain about the mysterious nonreals. Of course, 
this is no solution because this is may change the signs of the matrix 
elements in A1 if RF1 is not an identity matrix.
Thus, a suggestion on how to solve the problem is highly appreciated.

Dirk


Am 27.12.2011 04:14, schrieb Dirk Enzmann:
> I just encountered the problem that Mata gives me the error message
>
> invsym(): 3253 nonreal found where real required
> <istmt>: - function returned error
>
> although I believe that there is no nonreal value in the matrix.
>
> Below is the code that produces the error in the line
>
> W1 = A1*invsym(A1'*A1)
>
> Note that P1, S1, and A1 should contain the same values due to the fact
> that RF1 is an identity matrix - if I replace A1 by P1 Mata behaves as
> it should. If you ask why I use RF1 like that: I am testing whether the
> special case of a zero correlation is handled correctly - if I insert
> values such as .05 in the off-diagonal cells, Mata keeps complaining
> about nonreal values.
>
> Any suggestions for a solution of this problem?
>
> * -------- (start) ----------
> mata
> P1 = ( .43506, .44920 \
> .68702, .06891 \
> .77649, -.09335 \
> -.60949, .27331 \
> .02898, .65232 \
> -.16600, .43717 \
> .82794, -.04080 \
> .79320, -.11331 \
> -.04388, .62171 \
> .03556, .71095 \
> .08361, .75362 \
> -.23253, .58472 \
> .71299, -.20058 \
> -.19725, .55294 \
> .51660, .03276 )
> RF1 = ( 1.00, .00 \
> .00, 1.00 )
> S1 = P1*RF1
> S1
> V1 = NULL
> eigv1 = NULL
> eigensystem(RF1,V1,eigv1)
> A1 = S1*(V1:/sqrt(eigv1))*V1'
> A1
> rssqA1 = diagonal(A1*A1')
> rssqA1
> cssqA1 = diagonal(A1'*A1)
> cssqA1
> W1 = A1*invsym(A1'*A1)
> W1
> end
> * -------- (end) ------------
>
> Dirk
>
> ========================================
> Dr. Dirk Enzmann
> Institute of Criminal Sciences
> Dept. of Criminology
> Rothenbaumchaussee 33
> D-20148 Hamburg
> Germany
>
> phone: +49-(0)40-42838.7498 (office)
> +49-(0)40-42838.4591 (Mrs Billon)
> fax: +49-(0)40-42838.2344
> email: dirk.enzmann@uni-hamburg.de
> http://www2.jura.uni-hamburg.de/instkrim/kriminologie/Mitarbeiter/Enzmann/Enzmann.html
>
> ========================================
--
========================================
Dr. Dirk Enzmann
Institute of Criminal Sciences
Dept. of Criminology
Rothenbaumchaussee 33
D-20148 Hamburg
Germany

phone: +49-(0)40-42838.7498 (office)
       +49-(0)40-42838.4591 (Mrs Billon)
fax:   +49-(0)40-42838.2344
email: dirk.enzmann@uni-hamburg.de
http://www2.jura.uni-hamburg.de/instkrim/kriminologie/Mitarbeiter/Enzmann/Enzmann.html
========================================
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