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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ptaylor
June 20, 2018 08:15AM
Hi, Taek-

Looking at the code, it appears that that FFT implementation is optimized for speed, so the input time series are zero-padded up to "powers of 2 combined with powers of 3 and 5 (no more than 3^3 and 5^5, though)." Note that hte output file's "TR" info has the appropriate physical frequency value (in Hz) corresponding to the upsampled time series. Do you need the spectral values at specific frequencies?

Note also that the type of the numbers in the output volumes is "complex", so if you wanted amplitudes, for example, you would perhaps want to use 3dcalc: 
3dcalc -a FILE -expr 'abs(a)' -prefix AMPS.nii.gz

--pt
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Subject Author Posted

3dDFT question

Hyuntaek June 19, 2018 04:07PM

Re: 3dDFT question

ptaylor June 20, 2018 08:15AM

Re: 3dDFT question

Hyuntaek June 20, 2018 11:06AM

Re: 3dDFT question

ptaylor June 21, 2018 07:29AM

Re: 3dDFT question

Hyuntaek June 21, 2018 05:27PM

Re: 3dDFT question

ptaylor July 04, 2018 02:33PM

Re: 3dDFT question

Hyuntaek July 05, 2018 03:13PM