[Eeglablist] Possible bug or hidden feature in pop_reref

[Alexandre Lehmann]

 Hello,

Sorry if this has been fixed already but I came across a tricky index issue
in eeglab 09.0.4.4b using pop_reref.

Say that I have 4 channels :

1 VEOG (bipolar)
2 M1
3 Fz
4 Cz

If I want to re_reference my data to M1, but not modify my EOG channel and
remove my new reference (M2) from the channels.

I type
 EEG = pop_reref( EEG, 2 ,'exclude',1,'keepref','off');

What happens in that case, is that data gets re_referenced to Fz (which is
channel 3, but the second non-excluded channel).
But then the channel that is actually removed is M2 (channel 2).

I kept wondering why I was left with an empty Fz after re-ref, which made
the kurstosis rejection crash.

So as I said in the title, I am not sure this is really a bug an tricky
index gymnastics

Most people don't have to face this this EOG channels are usually at the
end. It just so happened that I made some recordings with a custom mapping
of single electrodes.

If you are in a similar situation you can just reference by hand, or use a
similiar workaround :

        EEG = pop_reref( EEG, ref_chans-1 ,'exclude',1,'keepref','on');
        EEG = pop_select( EEG,'nochannel',ref_chans);

Best Regards

Alex

-- 
Alexandre Lehmann, Phd
Postdoctoral research fellow
Laboratory for Brain, Music & Sound Research
BRAMS - Université de Montréal
Pavillon 1420 boul. Mont Royal
Case Postale 6128, Station Centre-Ville
Montreal (QC)  H3C 3J7
Tel. (514) 343-6111 poste 28306
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