Planar representation for CTF data

  • MNE version: e.g. 0.24.0
  • operating system: e.g. macOS 12

Dear MNE users/developers,

When I load CTF MEG data on MNE, axial gradiometers are detected as MAG. Then to obtain planar representation (similar to ft_megplanar function) as described in
https://mne.tools/dev/auto_examples/preprocessing/virtual_evoked.html
I get the following error:

evoked.as_type('grad')

ValueError: No channels matching the destination channel type found in info. Please pass an evoked containingboth the original and destination channels. Only the locations of the destination channels will be used for interpolation.

My question is how I can obtain planar representation for CTF data?

Many thanks in advance,
Best,
Keyvan