Hi Andreas,
I'm afraid I don't know how the SPM filter works so I can't
comment on that, but the use of -1 in the call from melodic
just means that that filtering is to be ignored. In the
help for ip it says:
-t <hp_sigma> <lp_sigma> : Bandpass temporal filtering; nonlinear
highpass and Gaussian linear lowpass (with sigmas in volumes, not
seconds); set either sigma<0 to skip that filter
So it is the use of sigma<0 to skip the filter which is being used.
Hope that helps a little,
Mark
On 7 Oct 2004, at 07:38, Andreas Bartsch wrote:
> Hi folks;),
>
> there seems to be a fundamental difference of the hp-filtering as
> implemented in FSL & SPM. Could someone please elaborate a bit on the
> details? Is there a simple rule of thumb how a given hp-filter cutoff
> (in [secs]) translates into a corresponding value of the other
> package? Or is there a more profound difference in the characteristics
> of the filtered signal?
> Also: ip offers the option to low-pass filter data. By default,
> melodic seems call it at "-1". Is the kernel specified in negative
> values?
> Thanks + best regards-
> Andreas
>
>
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