[Eeglablist] MATLAB and BIOPAC Issues

[James Desjardins]

Hi Matthew,

The absolute units issue that you are having with your Matlab FFT  
script seems to be related to the fact that Matlab does not scale the  
output of the FFT by the length of the input. You may have to divide  
the abs output of your FFT by the number of points in your input  
vector. See a description her:

http://www.mathworks.com/support/tech-notes/1700/1702.html


James Desjardins
Technician, MA Student
Department of Psychology, Behavioural Neuroscience
Cognitive and Affective Neuroscience Lab
Brock University
500 Glenridge Ave.
St. Catharines, ON, Canada
L2S 3A1
905-688-5550 x4676


Quoting Matthew Facciani <facciamj at westminster.edu>:

> Hello All,
>
> I am trying to conduct analyses on my EEG data but I keep running   
> into problems. I used BIOPAC software to collect my data and I'm   
> trying to find asymmetry values from doing the analyses of FFT,   
> spectral analysis, and a log function. However, when I wrote a   
> program to run these analyses via MATLAB I obtain numbers much   
> higher than the literature suggests. I've conducted the analyses   
> verbatim from previous articles but all the other articles have used  
>  another software for data collection (namely neuroscan). Is there   
> something about BIOPAC that could alter MATLAB analysis? I also ran   
> into problems when I was using EEGLAB. Is there a certain procedure   
> I should do to convert my BIOPAC files (.acq) into something MATLAB   
> can read? Saving the files as .mat and .txt didn't work for EEGLAB,   
> and I couldn't figure out the correct functions using MATLAB to   
> accurately analyze my data.
>
> I appreciate any feedback, thank you!
>