[Eeglablist] Activity Power Spectrum with funktion "pop_prop()"

Arnaud Delorme arno at ucsd.edu
Sat Nov 27 21:36:57 PST 2010


Dear Beatrice,

the EEGLAB function that computes spectrum produces by default a spectrum that only uses 15% of the data (to speed up computation). That is probably why you observe a different spectrum compared to your software. You may change the default to use 100% in the graphic interface or on the Matlab command line. Another reason could be that the parameters for computing the spectrum (window size, padding, and overlap between windows) are different.

Best regards,

Arno

ps: there was a bug a couple of years ago where the spectrum function was only using the first trial. This has been fixed in 2009 in all version including EEGLAB 6.03b.

On Nov 4, 2010, at 4:20 AM, Jobst Beatrice wrote:

> Dear All,
>  
> I have a question about plotting the activity power spectrum (frequency vs. power) with the function “pop_prop()”:
> I have a dataset, which has already been examined with another software, and now I want to compare the results with EEGLab. My problem is, that the calculations for the Power Spectrum in EEGLab produces completely different and also unrealistic results, the function values are completely different ones.
> Where could be the problem? Is it possible, that the results are wrong because I don’t have the Signal Processing Toolbox for Matlab? How can I face this problem without buying the toolbox? Can there be other reasons for the problem?
>  
> Thank you for your help!!
>  
> Best regards,
> Beatrice Jobst
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