# JacobiN problem

Miller, James V (CRD) millerjv at crd.ge.com
Mon Jun 14 13:01:35 EDT 1999

```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.

-----Original Message-----
From: Peter Everett [mailto:peverett at bwh.harvard.edu]
Sent: Monday, June 14, 1999 11:53 AM
To: vtkusers at gsao.med.ge.com
Subject: JacobiN problem

I am using vtkMath::JacobiN to get the principal axes & moments
from the covariance matrix of a set of points. The eigenvectors
that get returned appear to be the *transpose* of the correct
eigenvectors (i.e. (x0,x1,x2),(y0,y1,y2),(z0,z1,z2) rather than
(x0,y0,z0),(x1,y1,z1),(x2,y2,z2)). I tested it with a simple
3-point example, and found that the 3rd eigenvector was not
normal to the plane through the points.

Is this a known problem with a known patch that I can get?

Thanks,
Peter C. Everett

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