[Camino-users] Eigensystem issue monotensor fitting

[Philip A Cook]

Hi,

First let's check you have the right components, please see

  http://cmic.cs.ucl.ac.uk/camino//index.php?n=Main.Fileformats#toc10

If you run voxel2image, the component volumes are in the order shown in the table there.

If you can upload an example DT image, I might be able to help further.


On Oct 14, 2015, at 11:51 AM, Alessandro Calamuneri <alecalamuneri at gmail.com> wrote:

> Hi camino experts,
> 
> I got into troubles when analyzing eigensystem coming from a monotensor fitting (with semidefinite positiveness constraints)..
> 
> When creating rotation matrices associated to eigendecomposition, I can see that a lot of times I do not have a proper rotation, ie, determinant =-1.
> I tried both by considering eigensystem coming from dteig command, either by determining it with in-house scripts built in matlab based on dtfitting output.
> 
> Possible explenation are:
> 
> 1) it should work that way because, for instance, you reorder rotation matrix columns to get corresponding eigenvalues sorted from biggest to smallest;
> 2) it should work that way for whatever any other reason;
> 3) Problem is caused by bad fitting due to noise in my data.
> 4) May problem be related to some error in output bit representation? (I am using voxel2image specifying number of components to get the data); however I do not think this be the case..
> 
> I am asking because I am extracting quaternion representation out from rotation matrices., and a correct rotation data is crucial..
> 
> Best Regards,
> 
> Alessandro
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