[Mne_analysis] pick_types from epochs?

[Alexandre Gramfort]

hi Per,

>     I apologize if this is an obvious question: I would like to pick the
> channel types I read from an epochs file. In other words, I have created an
> Epochs structure from raw data and then stored the epochs to a file. The
> epochs are created using meg=True, but I would now like to operate only on
> the gradiometers, or meg='grad'. For evoked data this functionality appears
> to be provided by pick_types_evoked, which accepts an evoked structure and
> then returns another one with the requested channel selection. Is there a
> way to achieve the same functionality with epochs data?

there is no pick_types_epochs and we could add it. In the mean time you use
the pick_channels method from Epochs. Something like:

epochs = mne.read_epochs(...)
picks = mne.pick_types(epochs, meg='grad')
ch_names = [epochs.ch_names[k] for k in picks]
epochs. pick_channels(ch_names)

HTH
Alex