[Eeglablist] Plotting more than one difference wave on one plot

[Arnaud Delorme]

Dear Mary-Jane,

there is a solution to do this in the graphic interface (menu item "Plot > Sum/compare ERPs). Then you may check the option to subtract conditions. 

At the STUDY level, it is currently not possible to plot differences using the graphic interface. However, plotting differences from the command line is pretty easy. For example, after creating a STUDY and pre-computing ERP, you may calls the function that plots ERP in STUDY (assumes 2 conditions) on channel 'cz' (I copied the first line from the EEGLAB history)

[STUDY erpdata erptime]= std_erpplot(STUDY,ALLEEG,'channels',{'CZ'});
figure;
plot(erptime, mean(erpdata{1},2), 'r'); % plot first condition in red
plot(erptime, mean(erpdata{2},2), 'b'); % plot second condition in red
plot(erptime, mean(erpdata{2},2)-mean(erpdata{1},2), 'k-'); % plot difference in black dashed

That's it. Note that this is what erpdata contains

erpdata = 

    [750x12 double]
    [750x12 double]

It is 12 subjects 750 points and 2 conditions.
Best,

Arno

On 23 Aug 2013, at 19:46, Makoto Miyakoshi wrote:

> Dear Mary-Jane,
> 
> The default EEGLAB does not have a solution for it.
> 
> If you are trying to plot IC ERP and not channel ERP, please try my plugin (alpha version). Note this plugin is for STUDY level, but you can create STUDY with n=1. Unzip it and locate the folder under /eeglab/plugins and reboot eeglab.
> 
> I haven't tried it personally, but ERPLAB may do it.
> http://erpinfo.org/erplab
> 
> Sometimes something very fundamental is missing from EEGLAB... 
> 
> Makoto
> 
> 
> 2013/8/22 Budd, Mary-Jane S <mbudd at essex.ac.uk>
> Dear List,
> I would like some help on plotting difference waves. I would like to plot
> the difference of two conditions (C1 minus C2) and plot this difference wave
> on the same plot as the difference of two other conditions (A1 minus A2).
> Could someone tell me how to do this through the EEGlab GUI?
> Thank you,
> Mary-Jane
> 
> ----------------------
> Dr Mary-Jane Budd
> Senior Research Officer
> Department of Psychology
> University of Essex
> Wivenhoe Park
> Colchester CO4 3SQ
> UK
> 
> Room 4.726
> 
> http://www.essex.ac.uk/psychology/department/people/Budd.html
> 
> 
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> 
> -- 
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
> <std_erpcalc.zip>_______________________________________________
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