[Eeglablist] Extracting Power Values

[Arnaud Delorme]

Dear Marco,

if you use no option to compute spectrum, then the units are power density (10*log(microvolt^2)/Hz) because the STUDY function uses the spectopo function. If you use 'specmode', 'fft', when you computed the spectrum then the unit is power values (10*log(microvolt^2)). These two are proportional but I agree that they should be made consistent. We have entered a bug report.

Best regards,

Arno

On Sep 19, 2011, at 6:33 AM, Marco Montalto wrote:

> Dear all,
> 
> I have created a STUDY and pre-computed measures for power spectra using the default spectopo parameters ("fft"). My question is the following: the numerical values I extract using this code (example is with channel Fpz): 
> 
> [ STUDY specdata specfreqs] = std_specplot(STUDY, ALLEEG, 'channels', { 'Fpz' });
> 
> are power values or voltage or amplitude etc.?
> 
> If they are not power values can someone explain to me how I can extract power values as I need these to calculate ERD/ERS?
> 
> Thanks and regards,
> Marco
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