[Eeglablist] problem interpolating channels

[Arnaud Delorme]

Dear Jason,

you command 

EEG = pop_interp(EEG, ALLEEG.chanlocs, 'spherical');

is not necessarily ideal. I would do

EEG = pop_interp(EEG, eeg_mergelocs(ALLEEG.chanlocs), 'spherical');

because otherwise ALLEEG.chanlocs might expand into multiple parameters (in case you have more than 1 dataset). Also, you can always use the eeg_checkset() function to ensure the consistency of an EEG dataset.
Best,

Arno

On Jun 9, 2011, at 2:14 PM, Jason Satel wrote:

> Hi All,
> 
> I am having some issues interpolating channels using EEGLAB. This is  
> my first full ERP experiment so any help would be appreciated.
> 
> The problem is that when I run the interpolate function, it says, for  
> example,  "Interpolating 4 channels...", but then does not actually  
> update nbchan or the number of channels in EEG.data (although  
> sometimes it does work for some subjects, but I can't find a  
> difference between the datasets that work/don't work - although the  
> same datasets consistently work/don't work even if I restart the whole  
> analysis). It seems like the channel locations are getting 'lost' and  
> then cannot be replaced once channels are deleted.
> 
> My basic analysis procedure:
> 
> 1) import bdf file, & high/lowpass filters,
> 2) get channel locations ( EEG =  
> pop_chanedit(EEG,'lookup','/Applications/MATLAB_R2008a/toolbox/eeglab9_0_3_4b/plugins/dipfit2.2/standard_BESA/standard-10-5-cap385.elp');  
> ),
> 3) remove bad channels using visual inspection
>    (e.g., EEG = pop_select(EEG,'nochannel',{'P1' 'EXG7' 'EXG8'}); )
> 4) average, baseline correction & rereference to average
> 5) remove bad trials (+/- 75uV, but not eye movements)
> 6) run ICA and remove bad components (eye movement related)
> 7) interpolate missing electrodes
>    ( EEG = pop_interp(EEG, ALLEEG.chanlocs, 'spherical'); )
> 8) rereference, re-baseline correct, remove additional bad trials
> 9) plotting, stats..
> 
> Then, when I try to reference to the average on the datasets that  
> didn't interpolate properly, I get the following error:
> "eeg_checkset warning: number of channels different in data and  
> channel file/struct: channel file/struct removed
> Re-referencing ICA matrix
> Warning: Wrong channel indices, removing ICA decomposition
>> In pop_reref at 269
> ??? Undefined function or variable 'dsafdsf'.
> Error in ==> pop_reref at 270
>             dsafdsf "
> 
> Cheers,
> Jason Satel
> 
> 
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