[Eeglablist] filtering data

Arnaud Delorme arno at salk.edu
Wed Feb 9 17:20:03 PST 2005


>I am trying to band pass filter my eeg data between 1 and 30 Hz.  I noticed that EEGlab uses a fourier transoform and what appears to be an ideal band pass filter. I have some experience using such a method to filter digital images for stimuli, and found that I get 'ringing' in the image using ideal filter functions.  Might this be the case while filtering one dimensional eeg data?  Might it be advisable to use a butterworth function? Basically what I am wondering is this: does eeglab use the fourier filter because I do not have matlab's signal processing toolbox? 
>
Yes it does. I programmed this filter because it was a better 
alternative than no filtering at all for users who do not have the 
signal processing toolbox. I observed that with this type of filter the 
signal drop-off was not as high as with standard FIR filtering. I do not 
know about ringing. The best alternative to it might be to buy the 
signal processing toolbox?

Arno
-- 

*Arnaud Delorme, Ph.D.*
Swartz Center for Computational Neuroscience, INC, University of San 
Diego California
La Jolla, CA92093-0961, USA

*Tel* :/(+1)-858-458-1927 ext 15/
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*Web page*: sccn.ucsd.edu/~arno <http://www.sccn.ucsd.edu/%7Earno>
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