[FieldTrip] 60 Hz notch using preprocessing

[Stanley Klein]

Francesco,
Have you actually looked at the FFT of the raw data? That will tell you what
needs to be removed. You might have line noise at one frequency and monitor
noise at a neighboring frequency.
Stan

On Fri, Oct 28, 2011 at 3:15 AM, Roemer van der Meij <
r.vandermeij at donders.ru.nl> wrote:

>  Hi Francesco,
>
> Just as a small add to Eelke's reply, you can specify a bs-filter for
> several ranges at once by doing it in a matrix, e.g.:
> cfg.bsfreq = [58 62; 118 122];
> Note though, these filters (at least the standard butterworth) get
> increasingly inaccurate (less sharp filter-response, more
> 'filter-rolling'/edge-artifacts) when going to higher frequencies, if you
> are using the same frequency-range-width.
>
> Best,
> Roemer
>
>
>
> On 28-10-11 10:36, Eelke Spaak wrote:
>
> Dear Francesco,
>
> A notch filter is referred to as a band-stop filter in
> ft_preprocessing's documentation, and is different from the
> (regression-based) DFT filter. To use a notch filter, specify:
>
> cfg.bsfilter = 'yes';
> cfg.bsfreq = [58 62]; % or whatever you deem appropriate
>
> Note that you will have to apply ft_preprocessing repeatedly if you
> explicitly want to filter out the harmonics of the line noise as well.
>
> Best,
> Eelke
>
> 2011/10/28 Francesco Di Pompeo <f.dipompeo at unich.it> <f.dipompeo at unich.it>:
>
>  Dear all,
>
> I need a 60 Hz notch filter before the ICA of continuous 4D data.
> I did it using ft_preprocessing but the 60 Hz line is still there..
>
> Something wrong in my script?
>
>
> cfg = [];
> cfg.dataset = '0';
> cfg.channel    = {'MEG', '-A246', '-A170', '-A110', '-A19'};
>
> cfg.bpfilter      = 'yes';
> cfg.bpfreq        = [1 150];
>
> cfg.dftfilter     = 'yes';
> cfg.dftfreq       = [60 120 180];
>
> data_meg                 = ft_preprocessing(cfg);
>
>
>
>
> -----------------------------------------------------------------
> Francesco Di Pompeo, PhD
> Institute of Advanced Biomedical Technologies and
> Department of Neuroscience and Imaging
> University of Chieti "G. d'Annunzio"
> Via dei Vestini - Campus Universitario
> 66013 Chieti - ITALY
> ph: +39-0871-3556907
> fax:+39-0871-3556930
>
>
>
> _______________________________________________
> fieldtrip mailing listfieldtrip at donders.ru.nlhttp://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>  _______________________________________________
> fieldtrip mailing listfieldtrip at donders.ru.nlhttp://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
> --
> Roemer van der Meij M.Sc.
> PhD student
>
> Donders Institute for Brain, Cognition and Behaviour
> Centre for Cognition
> P.O. Box 9104
> 6500 HE Nijmegen
> The Netherlands
> Tel: +31(0)24 3655932
> E-mail: r.vandermeij at donders.ru.nl
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20111028/90a954c7/attachment-0002.html>