[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.
Best,
Esther
Data from 1 participant (it was also the case with other participants), 1 condition can be found here:
https://www.dropbox.com/s/8vjcfid5p1i0o2t/FTav.mat
load('FTav.mat')
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';
figure
ft_multiplotTFR(cfg, TFRav);
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