[Eeglablist] Inter-electrode distances

Simon-Shlomo Poil simonshlomo.poil at cncr.vu.nl
Thu Oct 7 23:12:13 PDT 2010

Hi Paul

There is a function in Joseph Dien's "ERP toolbox" call ep_closestchans that
does what you want.

Simon

On Oct 8, 2010 5:56 AM, "Arnaud Delorme" <arno at ucsd.edu> wrote:

Hi Paul,

what you probably want is the distance on the scalp of the electrodes.
Assuming a spherical model, for this you have to get the angle between the
two vectors pointing to each electrodes from the center of then head the
multiply by the radius of the sphere to get the distance on the sphere. I
would simply do the dot product of the 3-D Cartesian coordinates of each
vector, then compute the angle using argcos (inverse cosine function)
(divide by the dot product by the length of the two vector then do the
argcos function), then compute angle (in radian) times radius to get the
distance.

I have not tried it so I am not sure my fast reasoning is right (but it is a
start). More at

http://en.wikipedia.org/wiki/Dot_product

Hope this helps,

Arno

On Oct 7, 2010, at 1:18 PM, Paul Kieffaber wrote: > Hi all, > Is there an
easy way to compute inte...
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