Hi Jack. Yes, the program feat_model (which creates the model given the
design, including outputting the ratio _only if_ it faile test) could be
recompiled to always output this - you just need to find the relevant
printf statement and recompile....
The threshold is currently set at 5e-2 - the reason that we have talked
about different thresholds is that doing the test the way we do (via the
ratoi of min to max eigenvalues) isn't appropriate for all design types -
basically it's just more complicated than that. However, we're just now
working on a better test which takes into account the contrasts and
typical noise level etc - so watch this space.
Cheers.
On Wed, 20 Oct 2004, Jack Grinband wrote:
> Hi All,
> What exactly is FEAT's rank deficiency threshold? I searched through the list and various replies
> have listed e(-8), e(-6), e(-5), and e(-4) as "conservative" thresholds. There is 4 orders of
> magnitude between the smallest and largest of these. So, does that mean that the threshold
> depends on some other factors?
>
> Also, I'm having trouble finding the eigenvalue min:max ratio for each analysis. I couldn't find it in
> the log or design files. Is there any way I can get this information?
> thanks,
>
> jack
>
Stephen M. Smith DPhil
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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