[Mne_analysis] Restore a reference electrode

[Lorenzo Alfine]

Dear mne users,

we're recording EEG with a 64 electrodes cap, using Oz as reference.
The final data are in brainvision format and when I call raw.info, the list
chs has 64 items:
63 EEG and 1 STIM.
For further analysis reasons (topomaps etc.) I would like to reconstruct
the Oz channel,
so to have 64 EEG channels.

My idea was to use, after epoching:

mne.add_reference_channels(epochs_clean, 'Oz', copy=False)
epochs_clean.info['bads'] = ['Oz']
epochs_clean.interpolate_bads()

Does it make any sense or am I missing some fundamental theoretical issue?
(For example interpolating could introduce some redundant information).

Later I want to calculate an evoked object, so I thought about
re-referencing to average:

epochs_clean.set_eeg_reference(ref_channels=None)

but I get this error:
*Cannot add an average EEG reference projection since a custom reference
has been applied to the data earlier.*

So I thought to bypass the error using add_channels() but I believe that
this is not really what I'm looking for.

Thank you in advance for any help,

 LA

MSc student, University of Padova
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