Alan wrote:

> Correction - Excel is supposed to do an inverse of a matrix but I couldn't get
> minverse to work right. It kept giving me a scalar (single value) instead of
> a matrix. I ended up having to run the matrix part of the example in SAS.

I can help you on this point. (microsoft products are oh-so-intuitive . .)

To get the inverse of a matrix in excel, first enter the matrix in an n by
n square set of cells. Next, highlight the n by n square set of cells in
which you want to place the inverse of the matrix. In the upper left hand
cell, type (but don't hit return yet!):

=minverse(b3:d5)

(assuming the original matrix is contained in the group of cells with
upper left corner being cell b3 and the lower right corner beig cell d5).
Now, rather than simply hitting return (which will give you the upper left
hand member of the inverse matrix only) you mist use cntl-shift-enter.
(See? I told you it was intuitive!)

You can check your result by multiplying the inverted matrix by the
original. Highlight an n by n space where the product matrix will go, and
enter in the upper lefthand corner cell (again not hitting return yet!):

=mmult(b3:d5,f3:h5)

assuming the original matrix is in the space b3:d5 and the inverse is in
the space f3:h5 as defined above. Now hit cntl-shift-enter and you should
get an identity matrix.

Hope this helps!

- Pat



-- Patrick E. Fleming
-- Department of Chemistry
-- San Jose State University
-- pfleming@...