MRG, FIX: avoid spurious "showing first five" message

mne/io/pick.py

@@ -886,9 +886,10 @@ def _pick_data_or_ica(info, exclude=()):
 
 
 def _picks_to_idx(info, picks, none='data', exclude='bads', allow_empty=False,
-                  with_ref_meg=True):
+                  with_ref_meg=True, return_kind=False):
     """Convert and check pick validity."""
     from .meas_info import Info
+    picked_ch_type_or_generic = False
     #
     # None -> all, data, or data_or_ica (ndarray of int)
     #
@@ -920,7 +921,11 @@ def _picks_to_idx(info, picks, none='data', exclude='bads', allow_empty=False,
     if picks.ndim != 1:
         raise ValueError('picks must be 1D, got %sD' % (picks.ndim,))
     if picks.dtype.char in ('S', 'U'):
-        picks = _picks_str_to_idx(info, picks, exclude, with_ref_meg)
+        picks = _picks_str_to_idx(info, picks, exclude, with_ref_meg,
+                                  return_kind)
+        if return_kind:
+            picked_ch_type_or_generic = picks[1]
+            picks = picks[0]
     if picks.dtype.kind not in ['i', 'u']:
         raise TypeError('picks must be a list of int or list of str, got '
                         'a data type of %s' % (picks.dtype,))
@@ -939,10 +944,12 @@ def _picks_to_idx(info, picks, none='data', exclude='bads', allow_empty=False,
         raise ValueError('All picks must be < n_channels (%d), got %r'
                          % (n_chan, orig_picks))
     picks %= n_chan  # ensure positive
+    if return_kind:
+        return picks, picked_ch_type_or_generic
     return picks
 
 
-def _picks_str_to_idx(info, picks, exclude, with_ref_meg):
+def _picks_str_to_idx(info, picks, exclude, with_ref_meg, return_kind=False):
     """Turn a list of str into ndarray of int."""
     # special case for _picks_to_idx w/no info: shouldn't really happen
     if isinstance(info, int):
@@ -1027,6 +1034,9 @@ def _picks_str_to_idx(info, picks, exclude, with_ref_meg):
                            'picks for these')
     else:
         picks = np.array(all_picks[np.where(any_found)[0][0]])
+    if return_kind:
+        picked_ch_type_or_generic = not len(picks_name)
+        return picks, picked_ch_type_or_generic
     return picks
 
 

mne/viz/epochs.py

@@ -18,7 +18,6 @@
 
 from ..utils import (verbose, get_config, set_config, logger, warn, _pl,
                      fill_doc)
-from ..utils.check import _is_numeric
 from ..io.pick import (pick_types, channel_type, _get_channel_types,
                        _picks_to_idx, _DATA_CH_TYPES_SPLIT,
                        _DATA_CH_TYPES_ORDER_DEFAULT)
@@ -169,14 +168,12 @@ def plot_epochs_image(epochs, picks=None, sigma=0., vmin=None,
     if combine is not None:
         ts_args["show_sensors"] = False
 
-    if picks is None or not _is_numeric(picks):
-        picks = _picks_to_idx(epochs.info, picks)
-        if group_by is None:
-            logger.info("No picks and no groupby, showing the first five "
-                        "channels ...")
-            picks = picks[:5]  # take 5 picks to prevent spawning many figs
-    else:
-        picks = _picks_to_idx(epochs.info, picks)
+    picks, picked_ch_type_or_generic = _picks_to_idx(epochs.info, picks,
+                                                     return_kind=True)
+    if picked_ch_type_or_generic and group_by is None:
+        logger.info("No picks and no groupby, showing the first five "
+                    "channels ...")
+        picks = picks[:5]  # take 5 picks to prevent spawning too many figs
 
     if "invert_y" in ts_args:
         raise NotImplementedError("'invert_y' found in 'ts_args'. "

mne/viz/tests/test_epochs.py

@@ -137,6 +137,7 @@ def test_plot_epochs_image():
     """Test plotting of epochs image."""
     epochs = _get_epochs()
     epochs.plot_image(picks=[1, 2])
+    epochs.plot_image(picks='mag')
     overlay_times = [0.1]
     epochs.plot_image(picks=[1], order=[0], overlay_times=overlay_times,
                       vmin=0.01, title="test"