AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

History of AFNI updates  

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October 21, 2009 12:00PM
Hi Joe,

This is not a bug.

Either way, align_epi_anat.py is used to align the anat to the EPI,
as you have seen.

But the example states that with the -volreg_align_e2a option, the EPI
will be transformed to align with the anat along with motion alignment.
It does not happen in align_epi_anat.py, but in the volreg block. The
reason for putting the transformations together is to avoid the extra
interpolation.

It may take reading the help example a couple of times for it to sink in
(and reviewing the resulting script).

---

In "Soup to Nuts" 3dMEMA.R is not used, 3dANOVA3 is. 3dMEMA.R uses
the t-stats in the group analysis, while 3dANOVA3 just uses betas.
So your guesses here look correct. I see no inconsistency with that
lecture.

The reason it is not so good to warp statistics is because they are
not (maybe assumed to be) normally distributed. While t-stats are
pretty close to this, other statistics are not.

The problem comes from interpolation. When a warped voxel gets its
value from the 27 nearest neighbors for example, those 27 values are
averaged in some way. But it is not terribly valid to average a bunch
of F-statistics.

---

At any rate, it's nice to see that your AFNI version is up to date
and that you are working to read through a lot of the help! :)

- rick

Subject Author Posted

small afni_proc.py bug, question

Joe Paxton October 21, 2009 11:29AM

not an afni_proc.py bug

rick reynolds October 21, 2009 12:00PM