Re: [Gretl-users] Problem with matrix command
On Thu, 25 Sep 2008, Franck Nadaud wrote:
Finally is spotted the source of the error: the matrix per element
exponentiation seems to be falty. Try the small script :
matrix T = {1,0,0,0;0,0.5,0,0;0,0,1.5,0;0,0,0,0.125}
T
matrix S = inv(sqrt(T))
S
matrix V = T.^-0.5
V
There are two separate issues here:
1) the argument to the ".^" operator gets passed as 0.5 rather than -0.5.
This is a bug.
2) Even when the bug is fixed, you can't expect "T.^-0.5", since it
contains zeros, and 0^(-1/2) is not defined.
Riccardo (Jack) Lucchetti
Dipartimento di Economia
Università Politecnica delle Marche
r.lucchetti(a)univpm.it
http://www.econ.univpm.it/lucchetti