[FieldTrip] Empty array in coherence connectivity analysis

Rosa Taylor Beale TaylorBealeR at cardiff.ac.uk
Fri Mar 30 17:52:14 CEST 2018

Hi all,
I'm a final year undergraduate in Cardiff working on pain networks.
I have been trying to calculate coherence between 3 seed regions, however when I run the ft_connectivityanalysis, the labelcmb and cohspctrm arrays are empty (the channel labels don't look like they were read?). There is no error or warning messages that occur when running the command, so I am unsure why it is not running correctly.

First, I run ft_freqanalysis which seems to run fine:

cfg = []

cfg.method = 'wavelet';

cfg.output = 'pow';

cfg.toi = 0:0.05:2;

cfg.foi = [30:1:100];

time_freq= ft_freqanalysis(cfg, virtualchannel_raw);

time_freq =

label: {3x1 cell}
dimord: 'chan_freq_time'
freq: [1x71 double]
time: [1x41 double]
powspctrm: [3x71x41 double]
cfg: [1x1 struct]

Then I run the connectivity analysis and up with the empty output:

cfg = [];

cfg.method = 'coh';

cfg.channelcmb = {'pfcCont_seed' 'smc_seed'
                   'pfcIps_seed' 'smc_seed'
                   'pfcCont_seed' 'pfcIps_seed'};

coherence = ft_connectivityanalysis(cfg, time_freq);

coherence =

labelcmb: {0x2 cell}
dimord: 'chancmb_freq_time'
cohspctrm: [0x71x41 double]
time: [1x41 double]
freq: [1x71 double]
cfg: [1x1 struct]

>> coherence.labelcmb

ans =

   Empty cell array: 0-by-2

>> coherence.cohspctrm

ans =

   Empty array: 0-by-71-by-41

I have tried with fieldtrip versions 20161011 and 20171015 on matlab r2015a.

I've shown this to various people much more experienced at fieldtrip than I and we've all been a bit stumped!
Any ideas?
Many thanks
Rosa Taylor Beale

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