[FieldTrip] power line filter

Davide Rivolta drivolta81 at gmail.com
Wed Oct 5 10:03:37 CEST 2011


Dear Jan-Mathijs,

Attached is the picture of a subject where I applied you advice.

As you can see the problem is still there. Maybe I can solve it by changing
the filter order (I am using defaults values).

However I am thinking to use a band stop filter.

Thanks,

Davide

On Tue, Oct 4, 2011 at 3:18 PM, jan-mathijs schoffelen <
jan.schoffelen at donders.ru.nl> wrote:

> Hi Davide,
>
> If you pad up to 10 seconds, you may change the filterfreqs into:
>
> filterfreqs = [49:0.1:51 99:0.1:101 149:0.1:151].
>
> Notice the 0.1, rather than the 1. This is because a 10-second segment of
> data has an intrinsic frequency resolution of 0.1 Hz.
>
> Note that this may make the code rather slow to run. Wouldn't it more
> sensible then to use a bsfilter?
>
> Best,
>
> JM
>
>   On Oct 4, 2011, at 3:05 PM, Davide Rivolta wrote:
>
>
> Dear all,
>
> I am trying to get rid of the power line noise. I use the dftfilter as
> indicated on the website.
>
> This works very well for most of the subjects. However, for some of them, I
> still get the noise.
>
> My trials have a different lenght: between 500 ms until 3 seconds.
>
> This is the script I used.
>
>
>  filterfreqs = [49:1:51 99:1:101 149:1:151];
>
>     cfg.dftfilter      =  'yes';
>     cfg.dftfreq      = filterfreqs;
>     cfg.padding    = 10;
>
>     dataprepro_syn = ft_preprocessing(cfg);
>
>
> The pad of 10 is the same as another already published study that used the
> same task.
>
>
> Attached is a picture of the problem (blu is baseline, red is stimulus).
> This is the result of multitepering (dpss).
>
>
> Thanks for your help,
>
> Davide
>
>
>
>
> <FMA14_power_spectra1.png>_______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
>   Jan-Mathijs Schoffelen, MD PhD
> Donders Institute for Brain, Cognition and Behaviour,
> Centre for Cognitive Neuroimaging,
> Radboud University Nijmegen, The Netherlands
> J.Schoffelen at donders.ru.nl
> Telephone: +31-24-3614793
>
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>



-- 
Davide Rivolta, PhD
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20111005/91f09ef9/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: power_spectra1.png
Type: image/png
Size: 13305 bytes
Desc: not available
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20111005/91f09ef9/attachment.png>


More information about the fieldtrip mailing list