[FieldTrip] No backprojection following ICA (Peter Lyons)

Peter Lyons plyons at udel.edu
Thu Jun 11 15:59:59 CEST 2015

Hi Wanja,

Thanks for your quick response.  Just to clarify a few points:

We received the message "not applying the backprojection matrix to the
sensor description" because we do not have a 'tra' matrix defined.

Because we are using EEG data with a one to one relationship between the
number of channels and the number of electrodes, and therefore do not have
a need to define a 'tra' matrix (?), is it safe to assume that our call to
ft_rejectcomponent successfully recomposed our data?

If we do need to define a 'tra' matrix, when is the best time to do so?

I really appreciate your input.


On Wed, Jun 10, 2015 at 8:35 AM, Wanja Moessing <WanjaMoessing at gmx.de>

> Hi Peter,
> I get the same note. From a look into the code of ft_rejectcomponent it
> seems that, for EEG data, this note has to appear as long as you do not
> have a 'tra' matrix in your electrode description.
> The FAQ [
> http://www.fieldtriptoolbox.org/faq/how_are_electrodes_magnetometers_or_gradiometers_described]
> suggests that this 'tra' matrix should only be there if the channels are
> not exactly equal to your electrodes.
> Please correct me if I am wrong - I am not a FT developer.
> I agree that this message could be a little bit clearer.
> Kind regards,
> Wanja
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> fieldtrip at donders.ru.nl
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