JacobiN problem

[Miller, James V (CRD)]

Actually the interface to JacobiN is a float **v not a float *v[] (which muddles the interpretation
even further).

That being said, the eigenvectors are returned as the columns of this matrix (since this is pretty
much standard and is what the Numerical Recipes line of books uses).

Unfortunately, in your case you'll need to perform a copy/transpose.

Sorry for the confusion.


-----Original Message-----
From: Peter Everett [mailto:peverett at bwh.harvard.edu]
Sent: Monday, June 14, 1999 1:48 PM
To: vtkusers at gsao.med.ge.com
Cc: millerjv at crdns.crd.ge.com
Subject: RE: JacobiN problem


> Are you saying the eigenvectors are being returned as the rows or
> as the columns of the matrix?
> 
> It is pretty standard for eigenvectors to form the columns of a matrix.
> Is this what you are seeing?
> i.e. v[0][0] is the first element of the first eigenvector, v[0][1] is
> the first element of the second eigenvector, v[0][2] is the first element
> of the third eigenvector, etc.
> 
> This is the intention of the routine.  Let me know if this is not the case.

That would be fine if v were passed as a matrix. The interface to JacobiN
is an array of N eigenvectors ( float *v[]; ). One would therefore expect
v[0] to be the first principal axis, and v[N-1] to be the last (the normal
to the least-squares, best-fit hyperplane).

I understand the conflict between the two ways of passing a matrix, and
that often an NxN matrix is passed as N vectors of size N. In my case, I
am dealing strictly with vectors and have no matrices. My vectors are
stored individually, in non-contiguous memory, and loaded using v[0]=v0....
I would therefore expect v0 to be a solution to the eigenvector problem,
not an array of x coordinates.

-Peter C. Everett


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