I am using feat_model to generate my design matrix. I want to convolve the design with a custom impulse response function. To this end I pass a run0.fsf file to feat_model containing among other things:
```
set fmri(convolve1) 7
# Convolve phase
set fmri(convolve_phase1) 0
# Apply temporal filtering
set fmri(tempfilt_yn1) 1
# Add temporal derivative
set fmri(deriv_yn1) False
# Custom EV file
set fmri(custom1) "/home/chymera/NIdata/ofM.dr/_l1/composite_work/_subject_session_scan_4007.ofM_cF2.7_EPI_CBV/level1design/ev_e0_0_1.txt"
# Optimal/custom HRF convolution file
set fmri(default_bfcustom) "$/usr/share/fsl/etc/default_flobs.flobs/hrfbasisfns.txt"
set fmri(basisorth1) 1
set fmri(basisfnum1) 1
set fmri(bfcustom1) "/home/chymera/irf.txt"
```
I have come to this collection of variables by reading the FEAT UserGuide and trial and error. The latter was in particular needed for the basisorth1, basisfnum1, and bfcustom1 variables, which I could find no documentation for in either the FEAT UserGuide or the source code.
Could anyone please explain:
* what exactly these variables do
* why we need both a default_bfcustom and a bfcustom$i variable
* how one would handle multiple basis sets with this set-up (I assume the *$i variables are designed to do just that - but how?).
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