[Eeglablist] epoching for 2 consecutive marker events

[ANDREW HILL]

Jess - I suggest you look at event assignment / bin manipulation in ERPLAB - it's extremely straightforward and well documented - very straightforward to do conditional re-assigment of epoch bin/labels, etc.

best,
andrew


On Today 6:34 AM, jhartcher at tuebingen.mpg.de wrote: 

> 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
> 
> 
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