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Darren,<br>
<br>
the best way to process ERPs under EEGLAB is to create studies. This
way the ERPs are saved under separate files and loaded on the fly. They
are also stored in the STUDY structure under<br>
<br>
STUDY.changrp(X).erpdata<br>
STUDY.changrp(X).erptimes<br>
<br>
X represents the index of the channel (the structure also contains the
channel label). This can contain ERP for an arbitrary large number of
subjects (since the raw data is not in memory - only the ERP data is
present there - there is little memory limitation). Also, this
structure "erpdata" usually contains a cell array of ERP for different
conditions/groups. For more information, see the different fields of
the STUDY super-structure below<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.sccn.ucsd.edu/eeglab/clusttut/clustertut.html#studyset">http://www.sccn.ucsd.edu/eeglab/clusttut/clustertut.html#studyset</a><br>
<br>
You should try creating a simple study with a couple of subjects,
precompute the ERPs (using menu item "STUDY > Precompute data
measure"), plot them (so they are read in memory) and look at this
structure. The plotting option also allows you to compute basic
parametric and permutation statistics on ERPs.<br>
<br>
Note however, that you should not expect EEGLAB to be ideal for
processing ERP data the "standard ERP way". It was not designed in this
spirit.<br>
<br>
Hope this helps,<br>
<br>
Arno<br>
<br>
ps: the pop_comperp() function also computes ERP for different
conditions but it is obsolete and will not be used in the future.<br>
<br>
Darren Weber wrote:
<blockquote
cite="mid:b808b3510803051347k68382b55of291d71f31be071b@mail.gmail.com"
type="cite"><br>
What is the best way to calculate and process ERPs in EEGLAB?<br>
<br>
If I want to convert an epoch dataset to an ERP dataset, should I
simply change EEG.data to an Nchan x Nsamp matrix? For example:<br>
<br>
EEG.data = mean(EEG.data, 3);<br>
<br>
Can we store the variance somewhere? Do we have a data structure
separate from EEG.data, maybe EEG.avg that contains the mean, var,
Ntrials or Nepochs in the avg, etc? What is the best way to combine
ERP data across subjects?<br>
<br>
Best, Darren<br>
<br>
PS, I can do all this with custom scripts, but I want to know if there
is a specific EEGLAB way of doing all this.<br>
<br>
<pre wrap="">
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