afni.nimh.nih.gov

Hello,

I'm reading the notes of 3dFWHMx, which says
'If you don't want to go to that much trouble, use '-detrend' to approximately subtract out the anatomical spatial structure, OR use the output of 3dDetrend for the same purpose.'

I tried both option on my dataset. First I using 3dDetrend -polort 2 -prefix det dset, and using the output as input for 3dFWHMx. The programs ran successfully. But then I tried using detrend option directly, i.e., 3dFWHMx -detrend 2 -mask aaa -acf bbb -input dset. The program failed the model fitting and showed a list of calfun error.
The output plots are also quite different. I paste their google drivelink as follows, if you are interested, please take a look.



So, my question is the value following -detrend in 3dFWHMx and that following -polort 2 in 3dDetrend a different parameter? If so, what's the difference and is there any explanation for the shape of the plot from 3dFWHMx -detrend 2?

Best regard,
Zixun