[Eeglablist] epoching for 2 consecutive marker events

[Jess]

I want to select epochs based on whether marker S 1 is followed by a response marker S 4. I have 1000 S 1 markers but i only want to extract the 80 S 1 markers followed by S 4 markers, in a time window of [-200 500] . If I use the eeg_getepochevent.m function then I have the problem that it does not appear to be able to select the particular marker combinations that I need.

I have tried to write a separate loop to do this and then use the pop_epoch.m function but then I have the problem that the segmented data is not part of the EEG struct array anymore.

Is there a function that can do this? I think if I had to select the 80 conditional S 1 markers by hand this would not be optimal.

Maybe it is clearer what I want to do if you see my code in which I have loaded and filtered my .set data:

%%%%%%%%%%%%%%% Step 1: identify and extract marker times%%%%%%%%%%%%

n_events = length(EEG.event);

% declare empty arrays for storing event latencies
latency1 = [];
latency2 = [];

for go = 1:n_events

   % find S1/S2 and S4 combinations
   check1 = (strcmp(EEG.event(go).type, 'S  1') && strcmp(EEG.event(go+1).type, 'S  4'));
   check2 = (strcmp(EEG.event(go).type, 'S  2') && strcmp(EEG.event(go+1).type, 'S  4'));

   % store times at which combination S 1 & S 4 occurs
   if check1 == 1
       latency1 = [latency1; EEG.event(go).latency*1/EEG.srate];
   end

   % store times at which combination S 2 & S 4 occurs
   if check2 == 1
       latency2 = [latency2; EEG.event(go).latency*1/EEG.srate];
   end

end


%%%%%%%%%%%%%%%%%%%%%%%step 2 - not using EEGlab functions but epoching according to the Marker combinations%%%%%%%%%%
% S1
for go = 1:length(latency1)

   % retrieve marker time
   t_marker = latency1(go);

   % find indices of time vector
   ind_start = round((t_marker-200/1000)*EEG.srate)
   ind_end   = round((t_marker+500/1000)*EEG.srate)


   % add all data struct
   EEG_S1.epochs(go).data  = EEG.data(:, ind_start:ind_end);
   EEG_S1.epochs(go).times = [ind_start:ind_end].'*1/EEG.srate;



end


Thanks in advance.
jess