[FieldTrip] ft_channelrepair not finding electrodes

[Max Cantor]

Hi Jorn,

Sorry for the late response. I had to create a template for our cap, which
had it's own issues, but I think at this point I have it working. Even if
there are still some trigonometric issues, at the very least I have the
fieldtrip issue resolved.

For future reference, because I don't remember seeing anything on the
fieldtrip FAQ about this and it may be useful to somebody else, the
important thing is to turn the phi/theta from degrees into radians, and
then applying a trigonometric function to get the X, Y, and Z coordinates.

You can do all of these steps in 3 excel functions:

X = COS(RADIANS(Phi))*SIN(RADIANS(Theta))
Y = SIN(RADIANS(Theta))*SIN(RADIANS(Phi))
Z = =COS(RADIANS(Theta))

This link on the easycap website (
http://www.easycap.de/easycap/e/downloads/how_to_read_3d.htm) explains the
coordinate system.

I then typed up the channel name, x, y, and z coordinates in a four column
notepad document saved as a .sfp file, and used that as my cfg.elecfile.

Thank you for the support,

Max


On Mon, Nov 18, 2013 at 5:15 AM, "Jörn M. Horschig" <
jm.horschig at donders.ru.nl> wrote:

>  Hi Max,
>
> check out Fieldtrip/template/electrode and see if you can use one of the
> templates in there. Best would be to use electrode measurements that you
> actually performed yourself (to get the distances between electrodes
> right), but using a template might be good as well. Once you found a good
> template-file, you can set cfg.elecfile = 'folder/filename' and FieldTrip
> will handle the rest.
> Otherwise, if some of your colleagues have electrode measurements, you can
> also ask them for advice.
>
> Best,
> Jörn
>
>
> On 11/15/2013 5:40 PM, Max Cantor wrote:
>
> Hi all,
>
>  I'm trying to perform channel repair on EEG data that has undergone
> jump, muscle, and visual artifact rejection, and ICA to remove eog and ecg
> components, unmixed back into the original channels. It's a 61 channel
> system using a modified easycap layout and neighbours template.
>
>  The layout has been shown to work on topographic displays, and the
> template seems to work in that it creates a neighbours object when
> ft_prepare_neighbours is run on it without any errors.
>
>  However, I'm getting an error when I attempt to run ft_channelrepair:
>
> Error using ft_fetch_sens (line 179)
> no electrodes or gradiometers specified.
>
>  Error in ft_channelrepair (line 112)
>   sens = ft_fetch_sens(cfg, data);
>
>  I'm not currently using ft_datatype_sens or ft_read_sens, as I'm not
> really sure what elec/sens file I should be reading or how to go about
> creating it. I was hoping that the template, my data, and/or the layout
> would contain the necessary information, but given the error on
> ft_fetch_sens, that doesn't seem to be the case.
>
>  Any help on this issue would be greatly appreciated.
>
>  Thanks,
>
>  Max
>
>
> _______________________________________________
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>
>
>
> --
> Jörn M. Horschig
> PhD Student
> Donders Institute for Brain, Cognition and Behaviour
> Centre for Cognitive Neuroimaging
> Radboud University Nijmegen
> Neuronal Oscillations Group
> FieldTrip Development Team
>
> P.O. Box 9101
> NL-6500 HB Nijmegen
> The Netherlands
>
> Contact:
> E-Mail: jm.horschig at donders.ru.nl
> Tel:    +31-(0)24-36-68493
> Web: http://www.ru.nl/donders
>
> Visiting address:
> Trigon, room 2.30
> Kapittelweg 29
> NL-6525 EN Nijmegen
> The Netherlands
>
>
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