[Eeglablist] Global field power calculations

[Arnaud Delorme]

Data scaling in loadavg.m has been a long standing problem.

For information, I have now included Dr. Yang Zhang version into EEGLAB loadavg.m (loadavg_bcl.m was written from loadavg.m so it is still open source -- although we will consider removing it if Dr. Zhang has an objection for its inclusion in EEGLAB). There is now a flag that can toggle reading data using the old version or the new version (default).

Below, a link to compute GFP across trials (this you would need the data epochs not the data average)

http://sccn.ucsd.edu/pipermail/eeglablist/2008/002132.html

Thanks,

Arno

On Jun 24, 2012, at 11:23 PM, Stephen Politzer-Ahles wrote:

> Hi Mridula,
>  
> You can export .avg files directly into EEGLAB using the attached function (not my own creation--this is a function that Dr. Yang Zhang kindly shared with me). The syntax is like:
>  
> [signal, variance, chan_names, pnts, rate, xmin, xmax] = loadavg_bcl('some_neuroscan_file.avg');
>  
> (Note: EEGLAB also comes with a built-in function, loadavg(), that works in the same way. However, last time I checked, this function rescales the data, so the data that you have in MATLAB after import are not in microvolts but in some other units. If you want to work with data in microvolts, you can use the attached function.)
>  
> Once the data are in MATLAB, calculating global field power (both for individuals and across multiple individuals) is just arithmetic and can be done with some simple MATLAB scripting, it shouldn't need EEGLAB.
>  
> Best,
> Steve
> 
> 
>  
> On Mon, Jun 25, 2012 at 9:53 AM, Mridula Sharma <mridula.sharma at mq.edu.au> wrote:
> Hi,
> 
> We have data recorded from NeuroScan with 32 channels comparing 3 conditions within normal population. We would like to calculate and statistically compare the GFP for the 3 conditions.  
> 
> So can we export the .avg file to EEGlab and calculate and can this be done in individuals and across group. 
> 
> thanks
> Mridula
> 
> -- 
> Mridula Sharma, PhD
> Senior Lecturer and Program Convener
> Department of Linguistics
> Faculty of Human Sciences
> Room C5A 518
> Macquarie University
> NSW 2109 Australia
> 
> Tel: +61 2 9850 4863
> Email: mridula.sharma at mq.edu.au
> 
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> 
> -- 
> Stephen Politzer-Ahles
> University of Kansas
> Linguistics Department
> http://www.linguistics.ku.edu/
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