Dear Jing,
For some combinations of sampling rates and cutoff the Butterworth
filter may not be stable and that will generate NaNs. The latest SPM
version should give an error in these cases but previously you could
get NaNs as the output. In these cases you should try to either change
your cutoff frequency or reduce the filter order.
Best,
Vladimir
On Thu, Jun 16, 2011 at 10:27 AM, Jing Kan <[log in to unmask]> wrote:
> Dear SPMer,
>
> Thanks for concern!
>
> I've got a problem when I use the SPM for the MEG data preprocessing:
>
> With my data, if I "Epoch" first and "Filter" after, the data looks fine,
> and I can also visualize my data in time course or scalp by
> "dispay"-->"M/EEG" ; however, if I reverse the order to do the "filter"
> first with some band pass filter and then do "Epoch", the data generate
> lots of "NaN" and I can see nothing of MEG data in "dispay"-->"M/EEG". May
> I ask what possibility this problem might be coursed?
>
> Looking forward to your reply, and thanks in advance!
>
> Best,
>
> Jing
>
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