import os.path as op
import matplotlib.pyplot as plt

import mne

data_path = mne.datasets.sample.data_path()
fname = op.join(data_path, 'MEG', 'sample', 'sample_audvis-ave.fif')
evoked = mne.read_evokeds(fname, baseline=(None, 0), proj=True)

evoked_l_aud = evoked[0]

# restrict to magnetometers
evoked_l_aud.pick_types(meg='mag')

# pick the right channels
rt_chans = [k['ch_name'] for k in evoked_l_aud.info['chs']
            if k['loc'][0] >= 0]
rt_picks = mne.pick_channels(evoked_l_aud.info['ch_names'], rt_chans)

# make a dataset just of right channels.
evoked_l_aud_rt_chans = evoked_l_aud.copy()
evoked_l_aud_rt_chans.pick_channels(rt_chans)

# test plot_joint
evoked_l_aud.plot_joint(times=[0.089], show=False)
evoked_l_aud.plot_joint(times=[0.089], picks=rt_picks, show=False)
evoked_l_aud_rt_chans.plot_joint(times=[0.089], show=False)
plt.show()

# what about topo plot
evoked_l_aud.plot_topomap(times=[0.089], show=False)
evoked_l_aud_rt_chans.plot_topomap(times=[0.089], show=False)
plt.show()