# [FieldTrip] Choosing a subset of sensors with a uniform distribution over the head

"Jörn M. Horschig" jm.horschig at donders.ru.nl
Fri Sep 19 12:15:31 CEST 2014

```Hi Stephen,

there is no predfine FieldTrip way for this. You could try to this via
the neighbour template. If you know that the neighbours are well defined
and only the nearest neighbours are defined as neighbours (the
triangulation method might do that), you can loop through the neighbour
definition, and throw out all neighbours of channel i from the neighbour
definition, something like:

> for i=1:numel(neighbs)
>
> % find all neighbouring channels of channel i
> neighbbix = match_str(neighbs(i).neighblabel, {neighb(:).label});
>
> % throw them out
> neighb(neighbidx) = [];
>
> end

what you end up with is a neighbour structure with all channels that are
not adjacent to one another, i.e. a reduced number of channels. Not sure
if this works, but you might give it a try.

Best,
Jörn

On 9/19/2014 10:59 AM, Stephen Politzer-Ahles wrote:
> Hello,
>
> I am trying to plot a multiplot of MEG sensors over the head, but
> since I have over 200 sensors I don't want to plot them all (it
> becomes more or less illegible; see http://i.imgur.com/lT93i2T.png).
> What I would like to do is take half or even a third of the channels,
> and plot them at double or triple the size, as in
> http://i.imgur.com/6wcrNFS.png (which I created by just plotting the
> even-numbered channels). As you can see from this image, simply
> selecting the even-numbered channels in my array doesn't give a nice
> symmetrical or uniform distribution. Is there any way (for example,
> somehow using the neighbours structure) to decimate the channels or to
> otherwise choose a subset of channels that is uniformly distributed
>
> Thank you very much,
> Steve
>
>
> Stephen Politzer-Ahles
> New York University, Abu Dhabi
> Neuroscience of Language Lab
> http://www.nyu.edu/projects/politzer-ahles/
>
>
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--
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Neuronal Oscillations Group
FieldTrip Development Team

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

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