[FieldTrip] Frequency bins changed after ft_freqstatistics
silas_chiu at yahoo.com
Tue Aug 15 15:19:59 CEST 2017
Nice to meet you all. My name is Ho Ching Chiu, currently working at the language lab in Experimental Psychology, University of Bristol, for a project on sentence comprehension using EEG.
I tried to use ft_freqstatistics to do cluster-based permutation test, for a within-subject comparison of the power spectrum of 19 participants across 2 conditions. (Please refer to the codes below for more details.)Before this, I used ft_freqgrandaverage to conjugate the spectrum of all participants for each conditions, so the input data for the cluster-based permutation test (for each condition) is 4D (subj_chan_freq_time) and size(condition1.powspctrm) = [19 32 125 471].
There was no error / warning message in the process of running ft_freqstatistics. The problem is the frequency bins in the output data. The frequency bin of the input data is 1:1:125, and I expected the output(.stat .prob etc) will have the same dimension of 32 x 125 x 471. But what I get is 32 x 25 x 471, and the .freq of the output becomes 5:5:125, which is not expected.
Could anyone please advice if I have set anything wrong in the process? Or is this some inherent limitation of the ft_freqstatistics function? Your help is much appreciated. Thank you very much.
---------code start---------load condition1 load condition2
cfg = ;
cfg.channel = 'all';cfg.latency = 'all';cfg.frequency = 'all';
cfg.method = 'montecarlo';cfg.statistic = 'ft_statfun_depsamplesT'; cfg.correctm = 'cluster';cfg.clusteralpha = 0.05;cfg.clusterstatistic = 'maxsum';cfg.minnbchan = 2; cfg.tail = 0; cfg.clustertail = 0; cfg.alpha = 0.025; cfg.numrandomization = 5000;
load neighboursfile % some predefined thingscfg.neighbours = neighbours;
% cfg.design not relevant to this question, omitted for simplicity
[stat] = ft_freqstatistics(cfg, condition1, condition2);
save stat_cond1_cond2 stat;
Best regards,Ho Ching
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