add test for coverage and update docs

src/metpy/plots/declarative.py

@@ -1305,12 +1305,14 @@ class PlotObs(HasTraits):
       * time
       * fields
       * locations (optional)
-      * time_range (optional)
+      * time_window (optional)
       * formats (optional)
       * colors (optional)
+      * plot_units (optional)
       * vector_field (optional)
       * vector_field_color (optional)
       * vector_field_length (optional)
+      * vector_plot_units (optional)
       * reduce_points (optional)
     """
 
@@ -1397,14 +1399,14 @@ class PlotObs(HasTraits):
     plot_units.__doc__ = """A list of the desired units to plot the fields in.
 
     Setting this attribute will convert the units of the field variable to the given units for
-    plotting using the MetPy Units module, provided that units are attached to the DateFrame.
+    plotting using the MetPy Units module, provided that units are attached to the DataFrame.
     """
 
     vector_plot_units = Unicode(default_value=None, allow_none=True)
     vector_plot_units.__doc__ = """The desired units to plot the vector field in.
 
     Setting this attribute will convert the units of the field variable to the given units for
-    plotting using the MetPy Units module, provided that units are attached to the DateFrame.
+    plotting using the MetPy Units module, provided that units are attached to the DataFrame.
     """
 
     def clear(self):
@@ -1574,14 +1576,14 @@ def _build(self):
         if self.vector_field[0] is not None:
             vector_kwargs = {}
             vector_kwargs['color'] = self.vector_field_color
-            if self.vector_plot_units is not None:
-                vector_kwargs['plot_units'] = self.vector_plot_units
+            vector_kwargs['plot_units'] = self.vector_plot_units
             if hasattr(self.data, 'units') and (vector_kwargs['plot_units'] is not None):
                 u = (data[self.vector_field[0]][subset].values
                      * units(self.data.units[self.vector_field[0]]))
                 v = (data[self.vector_field[1]][subset].values
                      * units(self.data.units[self.vector_field[1]]))
             else:
+                vector_kwargs.pop('plot_units')
                 u = data[self.vector_field[0]][subset]
                 v = data[self.vector_field[1]][subset]
             if self.vector_field_length is not None:

src/metpy/plots/station_plot.py

@@ -185,6 +185,8 @@ def plot_parameter(self, location, parameter, formatter='.0f', **kwargs):
             How to format the data as a string for plotting. If a string, it should be
             compatible with the :func:`format` builtin. If a callable, this should take a
             value and return a string. Defaults to '0.f'.
+        plot_units: `pint.unit`
+            Units to plot in (performing conversion if necessary). Defaults to given units.
         kwargs
             Additional keyword arguments to use for matplotlib's plotting functions.
 
@@ -348,9 +350,6 @@ def _scalar_plotting_units(scalar_value, plotting_units):
             else:
                 raise ValueError('To convert to plotting units, units must be attached to '
                                  'scalar value being converted.')
-
-        # Strip units, CartoPy transform doesn't like
-        scalar_value = np.array(scalar_value)
         return scalar_value
 
     def _make_kwargs(self, kwargs):

tests/plots/test_declarative.py

@@ -841,7 +841,8 @@ def test_attribute_error_station():
         pc.draw()
 
 
-@pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.022)
+@pytest.mark.mpl_image_compare(remove_text=True,
+                               tolerance={'2.1': 0.407}.get(MPL_VERSION, 0.022))
 def test_declarative_sfc_obs_change_units():
     """Test making a surface observation plot."""
     data = parse_metar_file(get_test_data('metar_20190701_1200.txt', as_file_obj=False),
@@ -874,6 +875,42 @@ def test_declarative_sfc_obs_change_units():
     return pc.figure
 
 
+@pytest.mark.mpl_image_compare(remove_text=True,
+                               tolerance={'2.1': 0.09}.get(MPL_VERSION, 0.022))
+def test_declarative_multiple_sfc_obs_change_units():
+    """Test making a surface observation plot."""
+    data = parse_metar_file(get_test_data('metar_20190701_1200.txt', as_file_obj=False),
+                            year=2019, month=7)
+
+    obs = PlotObs()
+    obs.data = data
+    obs.time = datetime(2019, 7, 1, 12)
+    obs.time_window = timedelta(minutes=15)
+    obs.level = None
+    obs.fields = ['air_temperature', 'dew_point_temperature', 'air_pressure_at_sea_level']
+    obs.locations = ['NW', 'W', 'NE']
+    obs.colors = ['red', 'green', 'black']
+    obs.reduce_points = 0.75
+    obs.plot_units = ['degF', 'degF', None]
+
+    # Panel for plot with Map features
+    panel = MapPanel()
+    panel.layout = (1, 1, 1)
+    panel.projection = ccrs.PlateCarree()
+    panel.area = 'in'
+    panel.layers = ['states']
+    panel.plots = [obs]
+
+    # Bringing it all together
+    pc = PanelContainer()
+    pc.size = (12, 12)
+    pc.panels = [panel]
+
+    pc.draw()
+
+    return pc.figure
+
+
 def test_save():
     """Test that our saving function works."""
     pc = PanelContainer()