[Eeglablist] plot more than 2 conditions averaged across subjects

Ludo Max ludo.max at uconn.edu
Mon Mar 28 15:44:46 PST 2005

Hi all,

Another averaging question: ERPs are recorded from 6 subjects who each
completed 4 conditions. The continuous data (one file per subject per
condition) have been epoched in EEGLAB and then saved. So now I load all
the datasets (for convenience with the GUI, memory is not a problem in
this instance with small datasets) again into EEGLAB so that I have the
24 datasets loaded.

It would seem that it should be an easy task to plot in one single graph
the group average ERPs for each of the 4 conditions (i.e., one trace per
condition with each trace being the average of the 6 subjects in that
particular condition). 

In fact, using Plot | Sum/Compare ERPs, it is really easy to obtain this
plot for _two conditions at a time_: add the 6 numbers for the
individual subject data sets for condition 1 into "Datasets to add" and
click the corresponding "avg" checkbox, then add the numbers for the 6
individual subject data sets for condition 2 into "Datasets to subtract"
and click the corresponding "avg" checkbox. Easy enough. 

BUT: is there a way with the GUI to plot _all 4_ conditions as separate
traces while still averaging into each trace the 6 subject data sets
that belong to that condition? Or is the only option to first average
across subjects per condition from the command line, and then add those
6 already-group-averaged ERPS to "Datasets to add" and select the "all
ERPs" checkbox?

Thanks in advance,

Ludo Max

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