[Eeglablist] bad channel rejection based on spectrum (pop_rejchan, spectopo issue)

Jerry Zhu jerryzhu at siu.edu
Wed Jul 16 12:56:29 PDT 2014

Dear all,
Since version 12, EEGLAB has a new method of bad channel rejection based on
spectrum. We found it is very cool! However, during the process, I found
the frequency range seems irrelevant. Not sure whether it is a bug or
something else.

Here is what I did (in EEGLAB v13.3.2):
Tools-->Automatic channel rejection-->Measure to use: spectrum-->check the
normalization off-->absolute threshold -50 50
The frequency range is the tricky part: I can leave it empty (by default it
uses [1 EEG.srate/2]), or put [1 55], or [55 65]. They all give me the same
calculated measures. Critically I check the code of pop_rejchan:

measure1 = pop_spectopo(EEG, 1, [], 'EEG' , 'freqrange', [1 125],
measure2 = pop_spectopo(EEG, 1, [], 'EEG' , 'freqrange', [55 65],

Run them and check with isequal(measure1, measure2). They are the same!

As far as I know, if I use different freqrange, the result should be
different with my dataset.

Maybe some other users can confirm this. Thanks for your help!


Jian Zhu, M.A.
Brain and Cognitive Sciences
Department of Psychology
Southern Illinois University Carbondale
Web: http://zhupsy.com

We have two halves in the brain: left and right. Nothing is right in the
left. Nothing is left in the right.
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