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

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rick reynoldr
September 23, 2009 01:35PM
Hi Brenda,

These warnings can be ignored (via -GOFORIT).

The basic problem is simply that you have exactly 2 runs. In the case
of exactly 2 runs, the baseline regressors will be extremely collinear
(even though they may be orthogonal).

For example, with exactly 2 runs, the constant baseline terms will be
"perfectly" collinear, with an r value of -1, since they are effectively
negatives of each other, once the mean is removed.

The warnings seemed like they were all for the baseline (verified using
'1d_tool.py -show_cormat_warnings' on your X-matrix).

Adding -GOFORIT will be necessary, but not harmful.

Note that if your stimuli vary over subjects, you would want to verify
that the only issue is in the baseline for each subject.

- rick

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Subject Author Posted

collinearity in AM regression

Brenda Benson September 22, 2009 02:44PM

Re: collinearity in AM regression

rick reynoldr September 22, 2009 05:50PM

Re: collinearity in AM regression

rick reynoldr September 23, 2009 01:35PM