The routine you want to look at is DGEEV. But this is really complicated. I do
not advise you to do that.
You might want to develop your own 6by6 solver based on the QR algorithm
directly.
(Check any numerical linear algebra book.) For 6by6, this is not that hard
and most of the
recent development have been targeting larger sizes. The plain QR algorithm
from the 70s
is just fine for 6by6. So you reduce your matrix to Hessenberg form, find a
shift, apply a QR step
on the Hessenberg form, deflate when needed, etc. This is a standard project
for graduate students
when they take a Numerical Linear Algebra class. It is probably better to go
that road than to try to
translate the LAPACK code. J.
On Jul 20, 2012, at 1:50 AM, Roly Whear wrote:
Good Morning
I was wondering if you could help with some advice on which lapack routine I
should use for the following problem (the maths is getting a bit beyond me).
I'm looking to get the rigid body modes of a mass on a set of springs. Sorting
out the mass and stiffness matricies to get the characteristic equation has
been relatively straight forward which leaves me with a 6x6 non symmetric
matrix. All I'm after are the real Eigenvalues and vectors.
The plan is to rework the C or fortran code into VB in Excel if it will work.
Any advice gratefully received
Thanks
Roly Whear
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