"""
.. _tut-inverse-methods:

Source localization with MNE/dSPM/sLORETA/eLORETA
=================================================

The aim of this tutorial is to teach you how to compute and apply a linear
minimum-norm inverse method on evoked/raw/epochs data.
"""

import os.path as op

import numpy as np
import matplotlib.pyplot as plt

import mne
from mne.datasets import sample
from mne.minimum_norm import make_inverse_operator, apply_inverse

###############################################################################
# Process MEG data

data_path = sample.data_path()
raw_fname = op.join(data_path, 'MEG', 'sample',
                    'sample_audvis_filt-0-40_raw.fif')

raw = mne.io.read_raw_fif(raw_fname)  # already has an average reference
events = mne.find_events(raw, stim_channel='STI 014')

event_id = dict(aud_l=1)  # event trigger and conditions
tmin = -0.2  # start of each epoch (200ms before the trigger)
tmax = 0.5  # end of each epoch (500ms after the trigger)
raw.info['bads'] = ['MEG 2443', 'EEG 053']
baseline = (None, 0)  # means from the first instant to t = 0
reject = dict(grad=4000e-13, mag=4e-12, eog=150e-6)

epochs = mne.Epochs(raw, events, event_id, tmin, tmax, proj=True,
                    picks=('meg', 'eog'), baseline=baseline, reject=reject)

###############################################################################
# Compute regularized noise covariance
# ------------------------------------
# For more details see :ref:`tut-compute-covariance`.

noise_cov = mne.compute_covariance(
    epochs, tmax=0., method=['shrunk', 'empirical'], rank=None, verbose=True)

fig_cov, fig_spectra = mne.viz.plot_cov(noise_cov, raw.info)

###############################################################################
# Compute the evoked response
# ---------------------------
# Let's just use the MEG channels for simplicity.

evoked = epochs.average().pick('meg')
evoked.plot(time_unit='s')
evoked.plot_topomap(times=np.linspace(0.05, 0.15, 5), ch_type='mag',
                    time_unit='s')

###############################################################################
# It's also a good idea to look at whitened data:

evoked.plot_white(noise_cov, time_unit='s')
del epochs, raw  # to save memory

###############################################################################
# Inverse modeling: MNE/dSPM on evoked and raw data
# -------------------------------------------------
# Here we first read the forward solution. You will likely need to compute
# one for your own data -- see :ref:`tut-forward` for information on how
# to do it.

fname_fwd = data_path + '/MEG/sample/sample_audvis-meg-oct-6-fwd.fif'
fwd = mne.read_forward_solution(fname_fwd)

###############################################################################
# Next, we make an MEG inverse operator.

inverse_operator = make_inverse_operator(
    evoked.info, fwd, noise_cov, loose=0.2, depth=0.8)
del fwd

# You can write it to disk with::
#
#     >>> from mne.minimum_norm import write_inverse_operator
#     >>> write_inverse_operator('sample_audvis-meg-oct-6-inv.fif',
#                                inverse_operator)

###############################################################################
# Compute inverse solution
# ------------------------
# We can use this to compute the inverse solution and obtain source time
# courses:

method = "dSPM"
snr = 3.
lambda2 = 1. / snr ** 2
stc, residual = apply_inverse(evoked, inverse_operator, lambda2,
                              method=method, pick_ori=None,
                              return_residual=True, verbose=True)

###############################################################################
# Visualization
# -------------
# We can look at different dipole activations:

fig, ax = plt.subplots()
ax.plot(1e3 * stc.times, stc.data[::100, :].T)
ax.set(xlabel='time (ms)', ylabel='%s value' % method)

###############################################################################
# Examine the original data and the residual after fitting:

fig, axes = plt.subplots(2, 1)
evoked.plot(axes=axes)
for ax in axes:
    ax.texts = []
    for line in ax.lines:
        line.set_color('#98df81')
residual.plot(axes=axes)

###############################################################################
# Here we use peak getter to move visualization to the time point of the peak
# and draw a marker at the maximum peak vertex.

# sphinx_gallery_thumbnail_number = 9

vertno_max, time_max = stc.get_peak(hemi='rh')

subjects_dir = data_path + '/subjects'
surfer_kwargs = dict(
    hemi='rh', subjects_dir=subjects_dir,
    clim=dict(kind='value', lims=[8, 12, 15]), views='lateral',
    initial_time=time_max, time_unit='s', size=(800, 800), smoothing_steps=10)
brain = stc.plot(**surfer_kwargs)
brain.add_foci(vertno_max, coords_as_verts=True, hemi='rh', color='blue',
               scale_factor=0.6, alpha=0.5)
brain.add_text(0.1, 0.9, 'dSPM (plus location of maximal activation)', 'title',
               font_size=14)

# The documentation website's movie is generated with:
# brain.save_movie(..., tmin=0.05, tmax=0.15, interpolation='linear',
#                  time_dilation=20, framerate=10, time_viewer=True)

###############################################################################
# There are many other ways to visualize and work with source data, see
# for example:
#
# - :ref:`tut-viz-stcs`
# - :ref:`ex-morph-surface`
# - :ref:`ex-morph-volume`
# - :ref:`ex-vector-mne-solution`
# - :ref:`tut-dipole-orientations`
# - :ref:`tut-mne-fixed-free`
# - :ref:`examples using apply_inverse
#   <sphx_glr_backreferences_mne.minimum_norm.apply_inverse>`.
