[FieldTrip] ft_channelrepair with channel absent from data

Tom Marshall t.marshall at fcdonders.ru.nl
Sun Nov 25 16:04:09 CET 2012

Hi Trippers,

I'm having some difficulty reinterpolating some missing channels in my 
ctf275 data. These are 2 channels that were never recorded because the 
sensors in question were switched off.

Luckily, in the documentation for ft_channelrepair I find:

"*For reconstructing channels that are absent in your data*, please 
define  your neighbours by setting cfg.method='template' and call  
FT_PREPARE_NEIGHBOURS *without* the data argument:
cfg.neighbours = ft_prepare_neighbours(cfg);
This will include channels that are missing in your in the 

I dutifully define such a neighbours structure:


This structure of course contains all 275 MEG channels, including the 
ones that are missing from my data.

So I try to reinterpolate:
//% get the 'full' list of channel names//
//for i=1:length(n)//
//    allchans{i,:}=n(i).label;//
//% find the names of the channels that were not recorded//
//% repair//

this fails with:

/??? Error using ==> minus//
//Matrix dimensions must agree.//
//Error in ==> ft_channelrepair at 279//
//  d = sens.chanpos - repmat(c, numel(sensidx), 1);/

length(sensidx) is 301 and length(sens.chanpos) is 273, so the error 
makes sense. However at this point I get a bit stuck as 'sens' is 
created in line 104-108 by the function 'ft_fetch_sens' which I can't 
find! 'help ft_fetch_sens', 'which ft_fetch_sens' and 'edit 
ft_fetch_sens' all fail.

I guess I have several questions all at once:
1) Is it actually possible to reinterpolate MEG channels that were never 
recorded - eg because the channels were deactivated when the acquisition 
took place?
2) What might be causing the error I'm seeing?
3) Where is ft_fetch_sens?

Thanks for help with any of the above!

Tom Marshall, MSc.
Neuronal Oscillations Group, Donders Centre for Cognitive Neuroimaging
tel: +31(0)243668487
email: t.marshall at fcdonders.ru.nl
postal: PO Box 9101, 6500HB, Nijmegen, The Netherlands
visiting: Kapittelweg 29, 6525EN, Nijmegen, The Netherlands

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