[Eeglablist] How to convert continuous data to epoched data?

[Stephen Politzer-Ahles]

Hi Chung-yeon,

Are you sure? If it works correctly, EEG.data should be a three-dimensional
data structure (number of channels x number of samples x number of
trials)--you can check this by typing size(EEG.data) or ndims(EEG.data)at
the command line.

Once you've epoched, EEG.pnts, EEG.xmin, EEG.xmax, and EEG.times (and any
other time-related fields that I might be forgetting) will be reflecting
the time (or points) in one epoch, not the time (or points) in the whole
dataset. Which might be why your data look like it's just 3 seconds.

If it didn't work this way, we might need more information about the nature
of your event markers, and how you ran Extract Epochs, to figure out what
the problem is. My first guess would be there, if you have 20 different
event markers (instead of 20 repetitions of the same marker), you may have
selected just one event type instead of all of them; or even if it's 20 of
the same marker, you may have only selected the first event.

Best,
Steve



Stephen Politzer-Ahles
New York University, Abu Dhabi
Neuroscience of Language Lab
http://www.nyu.edu/projects/politzer-ahles/


On Sat, Sep 28, 2013 at 3:54 AM, Chung-yeon Lee <jamixlee at gmail.com> wrote:

> Extract Epochs (pop_epochs) makes the data has 3 seconds length.
> Is this right result?
> But I want 20trials(epochs) x 3sec(-1~2) data.
>  2013. 9. 28. 오전 4:52에 "Stephen Politzer-Ahles" <politzerahless at gmail.com>님이
> 작성:
>
> Hello Chung-Yeon
>>
>> From the GUI you can select Tools > Extract Epochs -- see
>> http://sccn.ucsd.edu/wiki/Chapter_05:_Extracting_Data_Epochs.
>>
>> Best,
>> Steve
>>
>>
>>
>> Stephen Politzer-Ahles
>> New York University, Abu Dhabi
>> Neuroscience of Language Lab
>> http://www.nyu.edu/projects/politzer-ahles/
>>
>>
>> On Fri, Sep 27, 2013 at 11:14 AM, Chung-yeon Lee <jamixlee at gmail.com>wrote:
>>
>>> I have continuous EEG data with 20 event markers.
>>> How to convert this data to epoched data with latency from -1 to 2?
>>> I found other epoched data has 3 dimensional data structure in
>>> 'EEG.data'.
>>> However mine is 2 dimensional data.
>>> Please anybody help me to solve this problem.
>>> Thank you!
>>>
>>> --
>>> *Chung-Yeon Lee
>>> *Biointelligence Laboratory
>>> Seoul National University
>>> +82-10-7510-7150
>>> http://bi.snu.ac.kr/~cylee
>>>
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>>
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