plotting power topomaps: ValueError: trans must be a Transform between head<->meg, got None

(MNE 0.20.dev0)

I get an error when trying to plot power topomaps for tfrs computed with mne.time_frequency.tfr_morlet:

 File "/home/sh254795/anaconda3/lib/python3.7/site-packages/mne/transforms.py", line 428, in _ensure_trans
    raise ValueError('%s None' % err_str)

ValueError: trans must be a Transform between head<->meg, got None

I traced it down to transforms.py, line 427 (in def _ensure_trans), where apparently my existing trans is not recognised as such:

not isinstance(this_trans, Transform)
True

this_trans
{'from': 1, 'to': 4, 'trans': array([[ 0.99812019, -0.06127739, -0.00142468,  0.00122047],
       [ 0.06122039,  0.99779153, -0.02579   ,  0.01071874],
       [ 0.00300188,  0.02565429,  0.99966681,  0.03850674],
       [ 0.        ,  0.        ,  0.        ,  1.        ]])}

Why is the trans not recognized? I can share the file if you need.

Thanks!

[larsoner]

Okay you’ll have to dig in a bit. Maybe do:

orig = info['dev_head_t']
info['dev_head_t'] = Transform(orig['from'], orig['to'], orig['trans'])

This might not work either, though, and require further work. I was mostly just trying to give you hints to get you enough to get started – but if you don’t want to debug this let me know and I can work on a PR directly

[SophieHerbst]

Thank you, that works!