Hi,
It is quite a simple tool so doesn't really have documentation yet.
Essentially it tried different filter cutoffs and calculates the
percentage
of retained power in the EVs of the design matrix. Once this goes below
a threshold (default is 99%) then it chooses the last value for which it
passed the threshold. However, it also has a lower limit on the period
of the cutoff (default 90s) to avoid it being too aggressive and
removing
information that the pre-whitening needs to work.
Note that the output is in seconds - just paste it into the FEAT GUI.
You are right about running it on design matrices with confound
regressors
in. It does not know about this and so doesn't do any adjustment.
You need
to save a design without these (no need to run anything in FEAT - just
save
the design from the GUI and use the *.mat file as input). Running it
on such
a subset (no confounds) is the best approach to use.
All the best,
Mark
On 5 Oct 2009, at 16:46, wolf zinke wrote:
> Hi,
>
> I came across the recently added and quiet handy tool cutoffcalc. Is
> there any documentation/reference how it determines the minimal
> period for the high pass filter? If I understand it correctly, it
> uses all regressors of the design matrix for the calculation. Hence,
> if I run it on the 'pure' design matrix I'll get different results
> than running it on the feat design matrix with motion and confound
> regressors added. I guess it is reasonable to apply cutoffcalc only
> on the regressors of interest. Do I need to generate a reduced model
> for this purpose or can I tell cutoffcalc to use only specified
> regressors for the calculation (or is it completely stupid to use a
> regressor subset)
>
> Thanks for all the help,
> wolf?
>
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