[Eeglablist] Averaging conditions in STUDY vs Command Line

[Nikola Vukovic]

Dear Arno,

All my conditions have the same number of trials, but I'm still getting 
different results using the two methods. How do I move between log and 
absolute power space in command line?

Best,
Nikola

> Arnaud Delorme <mailto:arno at ucsd.edu>
> 20 August 2013 07:12
> Dear Nikola,
>
> combining conditions will concatenate the trials for the 2 conditions. 
> So if you have the same number of trials in both conditions, the 
> result below should be equivalent. If you have different numbers of 
> trials, the result will differ (if you use combine, the result will be 
> the grand average of all the trials from both conditions - this will 
> not be the case if you average two ERSP). There are also some issues 
> of scaling. You should not average ERSP in log space, but in absolute 
> power space.
>
> Arno
>
>
>
> Nikola Vukovic <mailto:vukovicnikola at gmail.com>
> 19 August 2013 22:09
> Dear list,
>
> Until now, I assumed that selecting several conditions and combining 
> them into one condition (using the "combine selected values" in STUDY 
> design window) simply averages the given conditions. Once I got more 
> comfortable with command line scripting, I started averaging them 
> manually (by plotting the conditions separately, then averaging their 
> ersp data output. For example ersp_avg = (ersp{1,1} + ersp{2,1})/2). 
> However, I find that the outputs I get when manually averaging, and 
> when averaging variables in STUDY design are completely different 
> (compare http://cl.ly/image/0E010I0g1x21 and 
> http://cl.ly/image/3O01242E0b0M).
> Where does this difference come from? What exactly does the "combine 
> selected values" function do?
>
> Thank you,
> Nikola
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