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st: matrix inverse


From   Vivian Sibbaluca <vsibbaluca@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: matrix inverse
Date   Mon, 15 May 2006 20:13:25 -0700 (PDT)

I do have a problem in generating matrix inverse in
Stata, particularly generalized inverse. As far as I
know, gen inverse always exists. When I tried to
perform it in my matrix, which has a dimension of
960X960, the message was convergence not achieved. I
tried it using another matrix of the same size, it was
able to compute its inverse. The second matrix though
is a full rank matrix. Then I tried using the inv
command on the first matrix. Surprisingly, it was able
to compute the inverse. I was wondering what seems to
be the problem in the matginv command in Stata?

Since matginv does not always yield the g-inv of my
matrices, I have used the inv command since.
Unfortunately, I encountered another problem. In one
of my matrices, I encountered the error message
"matrix has missing values". I checked the content of
the matrix but it does not have any missing values. I
tried using the syminv command since the matrix is
symmetric and it yielded an inverse. If this is the
case, why cant inv compute for the inverse if syminv
can? 

The general question is, why cant matginv compute for
the inverse of a matrix if it should be the command to
yield the inverse of any matrix? 

I also used the matrank command to check on the ranks
of my matrices. It also gives the error message
"convergence not achieved" for matrices that it cant
compute the ginv. What could be the problem?

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