[FieldTrip] no coil pos for planar combined data

Kaelasha Tyler ktyler at swin.edu.au
Tue Oct 21 15:57:43 CEST 2014

Hi all,

I am having problems using ft_sourceanalysis with planar gradiometer data.

I am following a tutorial for beamforming with lcmv method (which I believe is a work in progress) found here:
Using planar gradiometer data is mentioned in the tutorial, although not in detail.

My problem:
The .avg field produced by time locking, is lost when combining planar gradiometers using 'ft_combineplanar'.
In this case, I am unable to to use 'ft_sourceanalysis' on combined planar gradiometer data.
I get the error: Reference to non-existent field 'avg'.

I reasoned that I may be able to keep the .avg filed if I combine the planar gradiometer data at the outset, prior to timelocking. But in this case, the gradiometer positions in data.grad does not include 'coilpos'. Eg, no data.grad.coilpos.
When calling 'ft_sourceanalysis' in this case, I get the error: Reference to non-existent field 'coilpos'.

Any suggestions?

If the .grad.coilpos was retained when I combined the planar gradiometer data at the outset, (after preprocessesing and prior to timelokcing) then I would be able to use ft_sourceanalysis on planar gradiometer combined data successfully.
Is that possible?

Thanks in advance! (and thank you to all previous very helpful responses on this list).

Kaelasha Tyler

PhD Candidate
Brain and Psychological Science Research Centre
Swinburne University of Technology

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