[MRG] Fix compare evokeds

mne/evoked.py

@@ -854,6 +854,18 @@ def grand_average(all_evoked, interpolate_bads=True):
     return grand_average
 
 
+def _check_evokeds_ch_names_times(all_evoked):
+    evoked = all_evoked[0]
+    ch_names = evoked.ch_names
+    for ev in all_evoked[1:]:
+        if not ev.ch_names == ch_names:
+            raise ValueError(
+                "%s and %s do not contain the same channels" % (evoked, ev))
+        if not np.max(np.abs(ev.times - evoked.times)) < 1e-7:
+            raise ValueError("%s and %s do not contain the same time instants"
+                             % (evoked, ev))
+
+
 def combine_evoked(all_evoked, weights):
     """Merge evoked data by weighted addition or subtraction.
 
@@ -892,14 +904,7 @@ def combine_evoked(all_evoked, weights):
     if weights.ndim != 1 or weights.size != len(all_evoked):
         raise ValueError('weights must be the same size as all_evoked')
 
-    ch_names = evoked.ch_names
-    for e in all_evoked[1:]:
-        assert e.ch_names == ch_names, ValueError("%s and %s do not contain "
-                                                  "the same channels"
-                                                  % (evoked, e))
-        assert np.max(np.abs(e.times - evoked.times)) < 1e-7, \
-            ValueError("%s and %s do not contain the same time instants"
-                       % (evoked, e))
+    _check_evokeds_ch_names_times(all_evoked)
 
     # use union of bad channels
     bads = list(set(evoked.info['bads']).union(*(ev.info['bads']

mne/io/pick.py

@@ -583,17 +583,33 @@ def pick_types_forward(orig, meg=True, eeg=False, ref_meg=True, seeg=False,
     return pick_channels_forward(orig, include_ch_names)
 
 
-def channel_indices_by_type(info):
-    """Get indices of channels by type."""
-    idx = dict((key, list()) for key in _PICK_TYPES_KEYS if
-               key not in ('meg', 'fnirs'))
-    idx.update(mag=list(), grad=list(), hbo=list(), hbr=list())
-    for k, ch in enumerate(info['chs']):
-        for key in idx.keys():
-            if channel_type(info, k) == key:
-                idx[key].append(k)
-
-    return idx
+def channel_indices_by_type(info, picks=None):
+    """Get indices of channels by type.
+
+    Parameters
+    ----------
+    info : instance of mne.measuerment_info.Info
+        The info.
+    picks : None | list of int
+        The indices of channels from which to get the type
+
+    Returns
+    -------
+    idx_by_type : dict
+        The dictionary that maps each channel type to the list of
+        channel indidces.
+    """
+    idx_by_type = dict((key, list()) for key in _PICK_TYPES_KEYS if
+                       key not in ('meg', 'fnirs'))
+    idx_by_type.update(mag=list(), grad=list(), hbo=list(), hbr=list())
+    if picks is None:
+        picks = range(len(info["chs"]))
+    for k in picks:
+        ch_type = channel_type(info, k)
+        for key in idx_by_type.keys():
+            if ch_type == key:
+                idx_by_type[key].append(k)
+    return idx_by_type
 
 
 def pick_channels_cov(orig, include=[], exclude='bads'):

mne/viz/epochs.py

@@ -160,6 +160,9 @@ def plot_epochs_image(epochs, picks=None, sigma=0., vmin=None,
         group_by = "type"
         combine = "gfp"
 
+    if combine is not None:
+        ts_args["show_sensors"] = False
+
     if picks is None:
         picks = pick_types(epochs.info, meg=True, eeg=True, ref_meg=False,
                            exclude='bads')