# RE: RE: RE: st: kronecker product - matsize

 From "Martin Halla" To Subject RE: RE: RE: st: kronecker product - matsize Date Tue, 01 Feb 2005 16:17:02 +0100

```thank you very much david,

martin h

-------------------------------------------
Martin HALLA
Department of Economics
Johannes Kepler University Linz
Altenbergerstr. 69
A-4040 Linz, Austria
Martin.Halla@jku.at

Tel.: +43-732-2468-8219
Fax: +43-732-2468-2-8219
http://www.econ.jku.at/
-------------------------------------------

>>> ddrukker@stata.com 02/01/05 4:01 pm >>>
Martin Halla <Martin.Halla@jku.at> wrote that - matrix glsaccum- only
solves
part of the problem.  Martin needs to compute

matrix B = inv((z*inv(z'z)*z'x)'*(inv(sigma)#In)*x) *	///
(z*inv(z'z)*z'x)'*(inv(sigma) # In)*y

which is difficult since z is N by p, x is N by k and y is N by 1.

Martin used -matrix accum- to compute

ZZ=z'z
ZX=z'x

yielding

matrix B = inv((z*inv(ZZ)*ZX)'*(inv(sigma)#In)*x) *	///
(z*inv(ZZ)*ZX)'*(inv(sigma) # In)*y

Defining

W = (z*inv(ZZ)*ZX)

cause the problem to become

B = inv(W'*(inv(sigma)#In)x)*W'(inv(sigma)#In)*y

which could computed using -matrix glsaccum-, if we had the variables
that
make up the matrix W.

To obtain W, Martin can let each column of inv(ZZ)*ZX be vector that we
will
call h.  Martin can then transpose h, so it is now a row vector, make
the
row names of h equal to names of the variables in z and then use
-matrix
score- to compute a new variable.  After doing this for each column of
inv(ZZ)*ZX, he will have created the variables in W

With the W variables in hand, Martin now needs to compute

W'(inv(sigma)#In)x
and

W'(inv(sigma)#In)y

which can be computed using -matrix glsaccum-.  (To get
W'(inv(sigma)#In)x
from -matrix glsaccum- include the W and the x variables in the varlist
and
then grab the upper-right block of the resulting matrix.)

-David
ddrukker@stata.com

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```