Simply EEGLAB

The EEG structure

Station 1 · Lesson 3 · EEGLAB 2026.1

In the GUI

Workspace EEG
EditEvent values
latency (sec) EEG.event
Cancel

Script

EEG.setname            % 'Continuous EEG Data'
EEG.nbchan             % 32 channels
EEG.srate              % 128 samples per second
EEG.pnts               % 30504 samples per channel
(EEG.pnts - 1) / EEG.srate   % 238.3047 seconds (same as EEG.xmax)
size(EEG.data)         % 32 30504
class(EEG.data)        % 'single'
EEG.data(1, 1:5)       % first 5 samples of channel 1 (microvolts)
{EEG.chanlocs(1:3).labels}   % 'FPz' 'EOG1' 'F3'
EEG.event(1).type      % 'square'
EEG.event(1).latency   % 129.0087 (in samples)
(EEG.event(1).latency - 1) / EEG.srate   % 1.0001 (in seconds)
isempty(EEG.icaweights)   % 1 (true)

Which value should I choose?

Field	What it stores	Unit	Value in `eeglab_data.set`
`EEG.nbchan`	Number of channels	channels	32
`EEG.srate`	Sampling rate	Hz	128
`EEG.pnts`	Number of samples per channel	samples	30504
`EEG.trials`	Number of segments (1 = continuous data)	segments	1
`EEG.xmin` and `EEG.xmax`	Time of the first and the last sample	seconds	0 and 238.3047 (last sample)
`EEG.times`	Time of each sample	milliseconds	from 0 to 238304.6875
`EEG.data`	The signal itself	microvolts	a 32 × 30504 matrix
`EEG.chanlocs`	Name and position of each channel	—	32 elements
`EEG.event`	Events: type and latency	latency in samples	154 events (80 `square` and 74 `rt`)
`EEG.icaweights`	ICA weights	—	empty

Check

size(EEG.data) gives 32 30504
(EEG.pnts - 1) / EEG.srate gives 238.3047, the same as EEG.xmax and as Epoch end (sec) in the main window (shown rounded as 238.305)
EEG.event(1).type gives 'square', and the converted latency gives about 1.0001 seconds, matching what you saw in Edit > Event values
numel(EEG.event) gives 154, matching the Events line in the main window

In the GUI

Script

Which value should I choose?

Check

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