[FieldTrip] channel combination problems

Wunderle, Thomas thomas.wunderle at esi-frankfurt.de
Fri May 31 11:42:03 CEST 2013

Hi all,

I'm new in fieldtrip and I try to get the cfg.channelcmb to work, because I want to plot the connectivity between the channels of different laminar electrodes,
let's say the connectivity between channel 1:24 and 25:38

I tried the following:
cfg           = [];
cfg.method    = 'mtmfft';
cfg.taper     = 'dpss';
cfg.output    = 'fourier';
cfg.tapsmofrq = 1;
freq          = ft_freqanalysis(cfg, data)

The output is:
>> freq
freq =
            label: {3x1 cell}
           dimord: 'rpttap_chan_freq'
            freq: [1x101 double]
            fourierspctrm: [500x3x101 double]
            cumsumcnt: [500x1 double]
            cumtapcnt: [500x1 double]
             cfg: [1x1 struct]

I then run

cfg           = [];
cfg.method    = 'coh';
cfg.channelcmb = {freq.label{1} freq.label{2};freq.label{2} freq.label{1}};
coh= ft_connectivityanalysis(cfg, freq);

And the output here is:

>> coh
coh =
       labelcmb: {2x2 cell}
       dimord: 'chan_freq'
       cohspctrm: [2x101 double]
        freq: [1x101 double]
        dof: 500
        cfg: [1x1 struct]

As you can seen, the output of dimord is 'chan_freq' so in the subsequent call of ft_connectivityplot I get an error message:

cfg           = [];
cfg.parameter = 'cohspctrm';
ft_connectivityplot(cfg, coh);

??? Error using ==> ft_connectivityplot at 99
the data should have a dimord of chan_chan_freq or chancmb_freq

If I use in ft_freqanalysis the cfg.method = 'powandcsd', cfg.channelcmb seems to have no effect at all,
the coherence is computed for all possible pairs.

I also don't understand the difference between "cfg.channelcmb" and "cfg.labelcmb"

Can you help me in how I should correctly use the cannelcmb and labelcmb options?

Thanks for your help,

Dr. Thomas Wunderle
Ernst Strüngmann Institute (ESI) for Neuroscience<http://www.ncbi.nlm.nih.gov/feed/rss.cgi?ChanKey=PubMedNews>
in Cooperation with Max Planck Society <http://www.ncbi.nlm.nih.gov/feed/rss.cgi?ChanKey=PubMedNews>
Deutschordenstrasse 46
60528 Frankfurt am Main, Germany
thomas.wunderle at esi-frankfurt.de<mailto:thomas.wunderle at esi-frankfurt.de>
Tel:   +49 69 96769 519
Fax:   +49 69 96769 555

Sitz der Gesellschaft: Frankfurt am Main
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Geschäftsführer: Prof. Dr. Pascal Fries

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