erplab_event_timeshift

ERPLAB function to shift the time of specific event codes given by the user.

Purpose

There exists ~20 ms delay between an event code and the onset of the LCD screen. We want to correct this delay, by shifting the stimulus-event codes later in time. All other event codes not specified by the user are kept at their original timepoints.

Input

• Continuous EEG dataset
• List of event codes to shift
• How much time to shift the event codes
• Method for rounding
  • floor
  • ceiling
  • nearest
• Warning flags for event codes that we unable to be shift (for various reasons)

Output

• Continuous EEG dataset with the user-specified event codes shifted

Example

eventcodes = {'22', '19'};
timeshift  = 0.015;
rounding   = 'floor';
outputEEG  = erplab_shiftevents_eeg(inputEEG, eventcodes, timeshift, rounding);

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Previous Research

• Related ERPLAB functions erptimeshift.m & eegtimeshift.m
• EEGLAB Forums: Event code shifting

I was wondering whether there is a possibility in eeglab to shift all event markers by 50 ms backwards in time?

for index = 1:length(EEG.event)
   EEG.event(index).latency = EEG.event(index).latency-0.05*srate;
end;
EEG = eeg_checkset(EEG, 'eventconsistency'); % check for out of bound events [ALLEEG EEG] = eeg_store(ALLEEG, EEG, CURRENTSET); % store dataset in ALLEEG eeglab redraw; % redraw GUI