More fixes to hue, cmap_kwargs.

xarray/plot/dataset_plot.py

@@ -30,13 +30,16 @@ def _infer_scatter_meta_data(ds, x, y, hue, add_legend, discrete_legend):
     if add_legend and not hue:
             raise ValueError('hue must be specified for generating a legend')
 
-    if hue and not _ensure_numeric(ds[hue].values):
+    if hue and add_legend and not _ensure_numeric(ds[hue].values):
         if discrete_legend is None:
             discrete_legend = True
         elif discrete_legend is False:
             raise ValueError('Cannot create a colorbar for a non numeric'
                              ' coordinate')
 
+    if not hue and add_legend is None:
+        discrete_legend = None
+
     dims = ds[x].dims
     if ds[y].dims != dims:
         raise ValueError('{} and {} must have the same dimensions.'
@@ -49,15 +52,17 @@ def _infer_scatter_meta_data(ds, x, y, hue, add_legend, discrete_legend):
 
     if hue:
         hue_label = label_from_attrs(ds.coords[hue])
+        hue_values = ds[x].coords[hue] if discrete_legend else None
     else:
         hue_label = None
+        hue_values = None
 
     return {'add_legend': add_legend,
             'discrete_legend': discrete_legend,
             'hue_label': hue_label,
             'xlabel': label_from_attrs(ds[x]),
             'ylabel': label_from_attrs(ds[y]),
-            'hue_values': ds[x].coords[hue] if discrete_legend else None}
+            'hue_values': hue_values}
 
 
 def _infer_scatter_data(ds, x, y, hue):
@@ -175,30 +180,40 @@ def scatter(ds, x, y, hue=None, col=None, row=None,
     figsize = kwargs.pop('figsize', None)
     ax = kwargs.pop('ax', None)
     ax = get_axis(figsize, size, aspect, ax)
+
+    kwargs = kwargs.copy()
+    _meta_data = kwargs.pop('_meta_data', None)
+
     if discrete_legend:
         primitive = []
         for label, grp in ds.groupby(ds[hue]):
             data = _infer_scatter_data(grp, x, y, hue=None)
-            primitive.append(ax.scatter(data['x'], data['y'], label=label))
+            primitive.append(ax.scatter(data['x'], data['y'], label=label,
+                                        **kwargs))
     else:
         data = _infer_scatter_data(ds, x, y, hue)
-        cmap_kwargs = {'plot_data': ds[hue],
-                       'vmin': vmin,
-                       'vmax': vmax,
-                       'cmap': colors if colors else cmap,
-                       'center': center,
-                       'robust': robust,
-                       'extend': extend,
-                       'levels': levels,
-                       'filled': None,
-                       'norm': norm,
-                       }
-        cmap_params = _determine_cmap_params(**cmap_kwargs)
+        if hue is not None:
+            cmap_kwargs = {'plot_data': ds[hue],
+                           'vmin': vmin,
+                           'vmax': vmax,
+                           'cmap': colors if colors else cmap,
+                           'center': center,
+                           'robust': robust,
+                           'extend': extend,
+                           'levels': levels,
+                           'filled': None,
+                           'norm': norm}
+            cmap_params = _determine_cmap_params(**cmap_kwargs)
+            cmap_kwargs_subset = dict(
+                (vv, cmap_kwargs[vv])
+                for vv in ['vmin', 'vmax', 'norm', 'cmap'])
+        else:
+            cmap_kwargs_subset = {}
+
         primitive = ax.scatter(data['x'], data['y'], c=data['color'],
-                               vmin=cmap_kwargs['vmin'],
-                               vmax=cmap_kwargs['vmax'])
+                               **cmap_kwargs_subset, **kwargs)
 
-    if '_meta_data' in kwargs:  # if this was called from map_scatter,
+    if _meta_data:  # if this was called from map_scatter,
         return primitive        # finish here. Else, make labels
 
     if meta_data.get('xlabel', None):

xarray/plot/facetgrid.py

@@ -327,9 +327,13 @@ def map_scatter(self, x=None, y=None, hue=None, discrete_legend=False,
             # None is the sentinel value
             if d is not None:
                 subset = self.data.loc[d]
-                mappable = scatter(subset, x=x, y=y, hue=hue,
-                                   ax=ax, **kwargs)
-                self._mappables.append(mappable)
+                maybe_mappable = scatter(subset, x=x, y=y, hue=hue,
+                                         ax=ax, **kwargs)
+                # TODO: better way to verify that an artist is mappable?
+                # https://stackoverflow.com/questions/33023036/is-it-possible-to-detect-if-a-matplotlib-artist-is-a-mappable-suitable-for-use-w#33023522
+                if (maybe_mappable
+                   and hasattr(maybe_mappable, 'autoscale_None')):
+                    self._mappables.append(maybe_mappable)
 
         self._finalize_grid(meta_data['xlabel'], meta_data['ylabel'])
 

xarray/tests/test_plot.py

@@ -1791,7 +1791,7 @@ def test_wrong_num_of_dimensions(self):
             self.darray.plot.line(row='row', hue='hue')
 
 
-class TestScatterPlots(PlotTestCase):
+class TestDatasetScatterPlots(PlotTestCase):
     @pytest.fixture(autouse=True)
     def setUp(self):
         das = [DataArray(np.random.randn(3, 3, 4, 4),