[FieldTrip] questions about topoplot and notch filter

Robert Oostenveld r.oostenveld at donders.ru.nl
Tue Apr 14 09:52:31 CEST 2015


Dear WanYu

Regarding your first question: I am not sure what you expected to see in the figure, and what you actually did see. Perhaps you should be using ft_connectivityplot instead. Note that the high-level plotting functions (the ones that take a cfg as first input) are only there to help you to get started with the figures, you can always plot the actual data yourself using low-level matlab functions and using the helper functions in the fieldtrip/plotting directory.

Regarding the second question, perhaps these address your question
http://www.fieldtriptoolbox.org/faq/why_is_there_a_residual_50hz_line-noise_component_after_applying_a_dft_filter 
http://www.fieldtriptoolbox.org/tag/filter?do=showtag&tag=filter

best regards,
Robert



On 14 Apr 2015, at 00:48, WanYu Hsu <wanyu at gazzaleylab.ucsf.edu> wrote:

> Hi community,
> Recently I am analyzing EEG dataset with only 20 channels and I am focusing on coherence between frontal and posterior electrodes in frequency domain.
> 
> I got two questions here:
> 
> 1. I wanted to topoplot the coherence between each pair of electrodes that we're interested in, and I tried the following script:
> 
> cfg                    = [];
> cfg.colorparam = 'plvspctrm';
> cfg.layout         = 'biosemi64.lay';
> cfg.foi =[4];
> ft_topoplotCC(cfg, plv_avg_stim);
> 
> The electrode layout and coherence we wanted to see were in the plot, but the plot did not show coherence related to FP1, FP2, and FPz. Am I doing something wrong? 
> 
> 
> 
> 2. I would like to apply notch filter to remove 6 Hz and first I tried
> 
> cfg.dftfilter ='yes';     
> cfg.dftfreq = [6] 
> but the 6Hz signal was still there.
> Then I also tried
> 
> cfg.bsfilter ='yes';
> cfg.bsfreq =[5 7];
> 
> This worked well to remove 6Hz signal, but it also affected 5Hz and 7Hz.
> 
> Is there any way to remove 6 Hz specificlly?
> 
> Any help would be appreciated. 
> 
> 
> 
> Best,
> 
> Wanyu Hsu
> 
> 
> 
> 
> 
> 
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> fieldtrip at donders.ru.nl
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