[FieldTrip] Changing density of channels in ft_topoplotER?

Inês P ipalma6 at msn.com
Wed Jul 27 12:18:43 CEST 2016

Dear community,

My name is Inês and I'm using fieldtrip to look at EEG data acquired from a 32-channel BioSemi using BCI2000 in my BCI experiment.

Currently I have been looking at the alpha band power over averaged trials in a particular condition, and to do that I have been using both ft_topoplotER and ft_multiplotER ().
My problem is that although my data has 32 channels (all specified under data.label), both plots only display a few main channels - 20 to be exact.
I'm including an example image of the layout and the corresponding topoplot. The same channels are shown in multiplot. Here's my code:

%preprocessing for each subject and extracting desired trials%
data_alltrials = ft_appenddata(cfg, data{:});

freq_cfg = [];
freq_cfg.channel = 'all';
freq_cfg.method = 'mtmfft';
freq_cfg.output = 'pow';
freq_cfg.taper  = 'hanning';
freq_cfg.keeptrials = 'yes';
freq_cfg.foi = foi;
freq_cfg.tapsmofrq = 1;
fft_alltrials = ft_freqanalysis(freq_cfg, data_alltrials);
disp('Preprocessing done.');

cfg = []; cfg.layout = layout;
layout = ft_prepare_layout(cfg, data_alltrials);
ft_layoutplot(cfg, data_alltrials)

cfg = [];
cfg.layout = 'biosemi32.lay';
channel = ft_channelselection({'all'},data_alltrials.label);
cfg.channel = channel;
cfg.colorbar = 'yes';
cfg.showlabels = 'yes';
figure(); ft_topoplotER(cfg, fft_alltrials);
figure(); ft_multiplotER(cfg, fft_alltrials);

So I guess my question is: is there a way to change the density of electrodes plotted, or even show them all?
Can someone tell me if there is something wrong with the cfg settings I use or if I am doing something wrong at any other place?
Looking forward to hear from you all!


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