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  

Previous Message Next Message
Message List New Topic Print View
|
Lee Friedman
October 01, 2003 11:26AM
Bob,

Thanks for the reply.

We have looked at the data before and after retrend as you suggest.

The data look as expected.

We would gladly send you some .1D files which show time curves before
the fourier filter, after the fourier filter plus retrending and after the fourier filter
with no retrending.

These .1D files would be from voxels that have a non-zero correlation when we do the fim on the retrended data but have a zero correlaton when we do the fim on the non-retrended data.

The key difference is that the non-retrended data are zero centered and thus, many
time points have negative intensities.

I suspect that it is the negative intensities that are causing the problem, although a correlation coefficient should not care if the data are zero centered or not. For some
reason though, the analysis seems to care. At least that is my current theory.

Lee
Reply Quote
RSS
Subject Author Posted

correlaton r = 0 if no retrend after fourier

Lee Friedman September 26, 2003 04:33PM

Re: correlaton r = 0 if no retrend after fourier

bob cox September 29, 2003 11:49AM

Re: correlaton r = 0 if no retrend after fourier

Lee Friedman October 01, 2003 11:26AM