[FieldTrip] Compute Time-Frequency Granger Causality with ft_connectivityanalysis

[laetitia.lalla at inserm.fr]

Hello fieldtrippers, 
first of all, thanks a lot for this collaborative mailing list. It
helped me a lot in the past and i hope you will be able to help me today
! 

I succesfully implemented the spectral granger causality thanks to this
FieldTrip tutorial :
http://www.fieldtriptoolbox.org/tutorial/connectivityextended. Now I'd
like to compute a Time-Frequency Map of my granger causality. Hence, I
used ft_freqanalysis with cfg.method  = 'mtmconvol' and cfg.output  =
'powandcsd' and the minimal code 
>cfg=[];
>cfg.method='granger';
>granger=ft_connectivityanalysis(cfg, freq); 
to compute the granger causality. 
However, when I run this code, Matlab bugs and stays "busy" for a while
until I terminate it, with the following error message : 

Operation terminated by user during ft_checkdata>fixcsd (line 1255)

In ft_checkdata (line 797)
    data = fixcsd(data, cmbrepresentation, channelcmb);

In ft_checkdata>fixcsd (line 1351)
  data = ft_checkdata(data, 'cmbrepresentation', 'full');

In ft_checkdata (line 797)
    data = fixcsd(data, cmbrepresentation, channelcmb);

In ft_connectivityanalysis (line 392)
          data = ft_checkdata(data, 'cmbrepresentation', 'full');

I can see in the help of the function checkdata the following : 
"cmbrepresentation  = sparse, full (applies to covariance and
cross-spectral density)". But I don't really understand what
"cmbrepresentation" do ... Maybe someone who had a similar problem in
the past can help me ? I think I'm missing some optional arguments that
I should add. 

Thanks a lot for your help. 

Regards, 

Laetitia Lalla 
PhD student in INMED, Marseille, France 
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