[FieldTrip] Strange output for ft_freqanalysis using wavelets?

Esther Eijlers eijlers at rsm.nl
Thu Jun 19 16:32:17 CEST 2014

Dear all,

I recently started working on time-frequency analyses, and my code is working.
However, it seems to me that something is going wrong;

Using the code below to calculate TFRs using wavelets, the output in .powerspectrum is in the range of hundreds and sometimes even up to a thousand (can also be seen from the plot).
Trying multitapers (also in the code below), the range seems to be more normal (maybe up to 20).

I cannot find out what I’m doing wrong (I guess such outcomes are impossible?).
I preprocessed the data in BVA and transferred it to FT structures, but that shouldn’t be a problem right?

A final question considers NaNs, is it true that ft_freqanalysis can not handle them, so that the output for elektrode 16 e.g. is set to NaN when it contained artefacts (i.e. NaNs in my case) in just one trial?

I would appreciate it a lot if anyone could help me out.

Data from 1 participant (it was also the case with other participants), 1 condition can be found here:


cfg = [];

%% wavelet

%cfg.keeptrials = 'yes'; %not when you want to use ft_freqgrandaverage and permutation testing thereafter

cfg.method     = 'wavelet';

cfg.width      = 7;

cfg.output     = 'pow';

cfg.foi        = 1:2:100;

cfg.toi        = -0.5:0.05:2.0;

%% OR multitapers


cfg.output     = 'pow';

cfg.method     = 'mtmconvol';

cfg.foi        = 1:2:100;

cfg.t_ftimwin  = 5./cfg.foi;

cfg.tapsmofrq  = 0.4 *cfg.foi;

cfg.toi        = -0.5:0.05:1.5;

cfg.pad        = 'maxperlen';


TFRav          = ft_freqanalysis(cfg, FTav);

% plot the results

cfg = [];

cfg.baseline     = [-0.5 0];

cfg.baselinetype = 'absolute';

cfg.zlim         = 'maxabs';

cfg.showlabels   = 'yes';

cfg.layout       = 'biosemi64.lay';

cfg.interactive  = 'yes';

cfg.colorbar     = 'yes';


ft_multiplotTFR(cfg, TFRav);

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