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hrf model onset bug? #306
Description
Hi all,
trying to use the hrf model module to make regressors with delayed onset:
import nipy.modalities.fmri.hemodynamic_models as hm
tr=2.15
plot(hm.glover_hrf(tr, oversampling=1.,time_length=200*tr,
gave the attached plot, so the expected delay of 100 frames is divided by the tr value, but I also wonder if the scaling of the hrf is correct as it seems that the problem is with this line:
https://github.com/nipy/nipy/blob/master/nipy/modalities/fmri/hemodynamic_models.py#L32
also maybe I am misunderstanding the doc, many thanks @bthirion for some insight on this.
Activity
bthirion commentedon Feb 6, 2014
On 04/02/2014 09:47, bpinsard wrote:
yes, the onset is supposed to be in s (sorry, the docstring is
incomplete). The idea is that it had to be a fixed value smaller than 0.
Note that this function should not be used directly. We should
underscore it.
What did you intend to do ?
Best.
Bertrand
bpinsard commentedon Feb 6, 2014
ok so it is to be used only as a kernel to regress a block design,
I was using it to create 1 hrf regressor per event.
but what I wasn't understanding is the fact that from time_stamps which units is seconds is subtracted a value in tr : onset (sec) / dt (sec)
thanks
bthirion commentedon Feb 6, 2014
If I get it right, I would specify one condition per trial, when calling
the make_dmtx() function.
HTH
Bertrand