[FieldTrip] Only 1 and Inf as output of ft_connectivityanalysis

[Lucia Melloni]

Hi jan-mathijs

Unfortunately I get the same result whether or not I remove the mean.
Best,
-- Lucía

On May 2, 2013, at 9:57 AM, jan-mathijs schoffelen <
jan.schoffelen at donders.ru.nl> wrote:

Hi Lucia,

Could you remove cfg.removemean = 'yes' and try again?

Best,

Jan-Mathijs

On Apr 29, 2013, at 2:38 AM, Lucia Melloni wrote:

Hi!
I am trying to calculate coherence using ft_connectivityanalysis, but
I am getting only ones and infinity as output in cohspctrm with all of
my data sets.

I first run ft_freqanalysis with
cfg.method = 'mtmfft';
cfg.taper = 'dpss';
cfg.output = 'fourier';
cfg.foilim = [1 45];
cfg.tapsmofrq = 1;
cfg.keeptrials = 'yes';
cfg.keeptapers = 'yes';
freq = ft_freqanalysis(cfg, data);

Whether I do or I do not specify cfg.channel and cfg.channelcmb here
does not seem to make a difference for my problem later on. The
spectra look absolutely fine.

I then run ft_connectivityanalysis with
cfg.method    = 'coh';
cfg.removemean= 'yes';
cfg.trials    = 'all';
cfg.feedback  = 'yes';
cfg.complex   = 'abs';
coh           = ft_connectivityanalysis(cfg, freq);

The cohspctrm looks like this:
val(:,:,1,1) =

    1   Inf   Inf   Inf   Inf   Inf   Inf   Inf   Inf   Inf   Inf
Inf   Inf   Inf (etc.)

I get the following warning during ft_connectivityanalysis

Warning: Divide by zero.

In ft_connectivity_corr at 103

 In ft_connectivityanalysis at 524
Warning: Divide by zero.

In ft_connectivity_corr at 104

 In ft_connectivityanalysis at 524

The same happens if I try to calculate PLV through ft_connectivityanalysis.
This is with Fieldtrip version 20130422 and 20130427, Matlab R2009a,
Windows 7 (64bit).

Any advice?
Thanks!
Lucia
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Jan-Mathijs Schoffelen, MD PhD

Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands

Max Planck Institute for Psycholinguistics,
Nijmegen, The Netherlands

J.Schoffelen at donders.ru.nl
Telephone: +31-24-3614793

http://www.hettaligebrein.nl

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