[FieldTrip] Empty array in coherence connectivity analysis

Tobias Staudigl tobias.stdgl at gmail.com
Fri Mar 30 18:00:49 CEST 2018

Hi Taylor,

First  specify
cfg.output = 'fourier'
cfg.output ='powandcsd'

in your ft_freqanalysis.

Then try ft_connectivityanalysis again.


Am 30.03.2018 17:53 schrieb "Rosa Taylor Beale" <TaylorBealeR at cardiff.ac.uk

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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