[FieldTrip] power line filter

[jan-mathijs schoffelen]

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>_______________________________________________
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> fieldtrip at donders.ru.nl
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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

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