Merge pull request #1349 from jthielen/0-12-patch-xarray-0-15-1

Backport convert_coordinate_units (xarray 0.15.1 fix) to 0.12.x

.travis.yml

@@ -49,7 +49,7 @@ matrix:
   include:
     - python: 3.6
       env:
-        - VERSIONS="numpy==1.13.0 matplotlib==2.1.0 scipy==1.0.0 pint==0.8 xarray==0.10.7 pandas==0.22.0"
+        - VERSIONS="numpy==1.16.0 matplotlib==2.1.0 scipy==1.0.0 pint==0.10.1 xarray==0.13.0 pandas==0.22.0"
         - TASK="coverage"
         - TEST_OUTPUT_CONTROL=""
     - python: "3.8-dev"
@@ -126,6 +126,7 @@ before_script:
 
 script:
   - export TEST_DATA_DIR=${TRAVIS_BUILD_DIR}/staticdata;
+  - export NUMPY_EXPERIMENTAL_ARRAY_FUNCTION=1;
   - if [[ $TASK == "docs" ]]; then
       pushd docs;
       make clean overridecheck html linkcheck O=-W;

docs/installguide.rst

@@ -9,11 +9,11 @@ In general, MetPy tries to support minor versions of dependencies released withi
 years. For Python itself, that means supporting the last two minor releases.
 
 * matplotlib >= 2.1.0
-* numpy >= 1.13.0
+* numpy >= 1.16.0
 * scipy >= 1.0.0
-* pint >= 0.8
+* pint >= 0.10.1
 * pandas >= 0.22.0
-* xarray >= 0.10.7
+* xarray >= 0.13.0
 * traitlets >= 4.3.0
 * pooch >= 0.1
 

examples/sigma_to_pressure_interpolation.py

@@ -33,9 +33,9 @@
 lon = data.variables['lon'][:]
 time = data.variables['time']
 vtimes = num2date(time[:], time.units)
-temperature = data.variables['temperature'][:] * units.celsius
-pres = data.variables['pressure'][:] * units.pascal
-hgt = data.variables['height'][:] * units.meter
+temperature = units.Quantity(data.variables['temperature'][:], 'degC')
+pres = units.Quantity(data.variables['pressure'][:], 'Pa')
+hgt = units.Quantity(data.variables['height'][:], 'meter')
 
 ####################################
 # Array of desired pressure levels

setup.cfg

@@ -39,10 +39,10 @@ setup_requires = setuptools_scm
 python_requires = >=3.6
 install_requires =
     matplotlib>=2.1.0
-    numpy>=1.13.0
+    numpy>=1.16.0
     scipy>=1.0
-    pint>=0.8
-    xarray>=0.10.7
+    pint>=0.10.1
+    xarray>=0.13.0
     pooch>=0.1
     traitlets>=4.3.0
     pandas>=0.22.0
@@ -52,7 +52,7 @@ where = src
 
 [options.extras_require]
 dev = ipython[all]>=3.1
-doc = sphinx>=2.1; sphinx-gallery>=0.4; doc8; m2r; netCDF4
+doc = sphinx<3.0; sphinx-gallery>=0.4; doc8; m2r; netCDF4
 examples = cartopy>=0.15.0; matplotlib>=2.2.0; pyproj>=1.9.4,!=2.0.0
 test = pytest>=2.4; pytest-mpl; pytest-flake8; cartopy>=0.16.0; flake8>3.2.0; flake8-builtins!=1.4.0; flake8-comprehensions; flake8-copyright; flake8-docstrings; flake8-import-order; flake8-mutable; flake8-pep3101; flake8-print; flake8-quotes; flake8-rst-docstrings; pep8-naming; netCDF4; pyproj>=1.9.4,!=2.0.0
 

src/metpy/calc/thermo.py

@@ -125,7 +125,7 @@ def potential_temperature(pressure, temperature):
     --------
     >>> from metpy.units import units
     >>> metpy.calc.potential_temperature(800. * units.mbar, 273. * units.kelvin)
-    <Quantity(290.96653180346203, 'kelvin')>
+    <Quantity(290.9665329591884, 'kelvin')>
 
     """
     return temperature / exner_function(pressure)

src/metpy/plots/station_plot.py

@@ -192,6 +192,8 @@ def plot_parameter(self, location, parameter, formatter='.0f', **kwargs):
         plot_barb, plot_symbol, plot_text
 
         """
+        if hasattr(parameter, 'units'):
+            parameter = parameter.magnitude
         text = self._to_string_list(parameter, formatter)
         return self.plot_text(location, text, **kwargs)
 
@@ -353,8 +355,6 @@ def _to_string_list(vals, fmt):
         if not callable(fmt):
             def formatter(s):
                 """Turn a format string into a callable."""
-                if hasattr(s, 'units'):
-                    s = s.item()
                 return format(s, fmt)
         else:
             formatter = fmt

src/metpy/xarray.py

@@ -137,13 +137,30 @@ def unit_array(self):
     @unit_array.setter
     def unit_array(self, values):
         """Set data values from a `pint.Quantity`."""
-        self._data_array.values = values.magnitude
+        try:
+            self._data_array.values = values.magnitude
+        except ValueError:
+            raise ValueError('Unable to set unit array to a dimension coordinate. Use the '
+                             'assign_coords method instead')
         self._units = self._data_array.attrs['units'] = str(values.units)
 
     def convert_units(self, units):
         """Convert the data values to different units in-place."""
         self.unit_array = self.unit_array.to(units)
 
+    def convert_coordinate_units(self, coord, units):
+        """Return new DataArray with coordinate converted to different units.
+
+        Notes
+        -----
+        Backported from MetPy 1.0.
+        """
+        new_coord_var = self._data_array[coord].copy(
+            data=self._data_array[coord].metpy.unit_array.m_as(units)
+        )
+        new_coord_var.attrs['units'] = str(units)
+        return self._data_array.assign_coords(coords={coord: new_coord_var})
+
     @property
     def crs(self):
         """Return the coordinate reference system (CRS) as a CFProjection object."""
@@ -517,7 +534,7 @@ def parse_cf(self, varname=None, coordinates=None):
             else:
                 var.coords['crs'] = CFProjection(proj_var.attrs)
 
-        self._fixup_coords(var)
+        var = self._fixup_coords(var)
 
         # Trying to guess whether we should be adding a crs to this variable's coordinates
         # First make sure it's missing CRS but isn't lat/lon itself
@@ -542,18 +559,23 @@ def parse_cf(self, varname=None, coordinates=None):
 
     def _fixup_coords(self, var):
         """Clean up the units on the coordinate variables."""
-        for coord_name, data_array in var.coords.items():
-            if (check_axis(data_array, 'x', 'y')
-                    and not check_axis(data_array, 'longitude', 'latitude')):
+        for coord_name, coord_var in var.coords.items():
+            if (check_axis(coord_var, 'x', 'y')
+                    and not check_axis(coord_var, 'longitude', 'latitude')):
                 try:
-                    var.coords[coord_name].metpy.convert_units('meters')
+                    var = var.metpy.convert_coordinate_units(coord_name, 'meter')
                 except DimensionalityError:  # Radians!
                     if 'crs' in var.coords:
-                        new_data_array = data_array.copy()
                         height = var.coords['crs'].item()['perspective_point_height']
-                        scaled_vals = new_data_array.metpy.unit_array * (height * units.meters)
-                        new_data_array.metpy.unit_array = scaled_vals.to('meters')
-                        var.coords[coord_name] = new_data_array
+                        new_coord_var = coord_var.copy(
+                            data=(
+                                coord_var.metpy.unit_array * (height * units.meters)
+                            ).m_as('meter')
+                        )
+                        new_coord_var.attrs['units'] = 'meter'
+                        var = var.assign_coords(coords={coord_name: new_coord_var})
+
+        return var
 
     class _LocIndexer:
         """Provide the unit-wrapped .loc indexer for datasets."""

tests/plots/test_declarative.py

@@ -485,7 +485,8 @@ def test_declarative_sfc_obs_changes():
     return pc.figure
 
 
-@pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.022)
+@pytest.mark.mpl_image_compare(remove_text=True,
+                               tolerance={'3.1': 9.771, '2.1': 9.771}.get(MPL_VERSION, 0.))
 def test_declarative_sfc_obs_full():
     """Test making a full surface observation plot."""
     data = pd.read_csv(get_test_data('SFC_obs.csv', as_file_obj=False),

tests/plots/test_skewt.py

@@ -16,7 +16,7 @@
 from metpy.units import units
 
 
-@pytest.mark.mpl_image_compare(tolerance=.02, remove_text=True, style='default')
+@pytest.mark.mpl_image_compare(tolerance=.0202, remove_text=True, style='default')
 def test_skewt_api():
     """Test the SkewT API."""
     with matplotlib.rc_context({'axes.autolimit_mode': 'data'}):
@@ -47,7 +47,7 @@ def test_skewt_api():
     return fig
 
 
-@pytest.mark.mpl_image_compare(tolerance=.027 if matplotlib.__version__ < '3.2' else 34.4,
+@pytest.mark.mpl_image_compare(tolerance=.0272 if matplotlib.__version__ < '3.2' else 34.4,
                                remove_text=True, style='default')
 def test_skewt_api_units():
     """#Test the SkewT API when units are provided."""
@@ -66,6 +66,9 @@ def test_skewt_api_units():
         skew.plot_moist_adiabats()
         skew.plot_mixing_lines()
 
+        # This works around the fact that newer pint versions default to degrees_Celsius
+        skew.ax.set_xlabel('degC')
+
     return fig
 
 
@@ -82,7 +85,7 @@ def test_skewt_default_aspect_empty():
     return fig
 
 
-@pytest.mark.skipif(matplotlib.__version__ < '3' or matplotlib.__version__ >= '3.2',
+@pytest.mark.skipif(matplotlib.__version__ < '3.2',
                     reason='Matplotlib versions generate different image sizes.')
 @pytest.mark.mpl_image_compare(tolerance=0., remove_text=False, style='default',
                                savefig_kwargs={'bbox_inches': 'tight'})

tests/plots/test_station_plot.py

@@ -83,7 +83,7 @@ def test_station_plot_replace():
     return fig
 
 
-@pytest.mark.mpl_image_compare(tolerance=0.00413, savefig_kwargs={'dpi': 300},
+@pytest.mark.mpl_image_compare(tolerance=0, savefig_kwargs={'dpi': 300},
                                remove_text=True)
 def test_stationlayout_api():
     """Test the StationPlot API."""
@@ -92,7 +92,7 @@ def test_stationlayout_api():
     # testing data
     x = np.array([1, 5])
     y = np.array([2, 4])
-    data = {'temp': np.array([32., 212.]) * units.degF, 'u': np.array([2, 0]) * units.knots,
+    data = {'temp': np.array([33., 212.]) * units.degF, 'u': np.array([2, 0]) * units.knots,
             'v': np.array([0, 5]) * units.knots, 'stid': ['KDEN', 'KSHV'], 'cover': [3, 8]}
 
     # Set up the layout
@@ -151,15 +151,15 @@ def test_station_layout_names():
     assert sorted(layout.names()) == ['cover', 'stid', 'temp', 'u', 'v']
 
 
-@pytest.mark.mpl_image_compare(tolerance=0.0072, savefig_kwargs={'dpi': 300}, remove_text=True)
+@pytest.mark.mpl_image_compare(tolerance=0, savefig_kwargs={'dpi': 300}, remove_text=True)
 def test_simple_layout():
     """Test metpy's simple layout for station plots."""
     fig = plt.figure(figsize=(9, 9))
 
     # testing data
     x = np.array([1, 5])
     y = np.array([2, 4])
-    data = {'air_temperature': np.array([32., 212.]) * units.degF,
+    data = {'air_temperature': np.array([33., 212.]) * units.degF,
             'dew_point_temperature': np.array([28., 80.]) * units.degF,
             'air_pressure_at_sea_level': np.array([29.92, 28.00]) * units.inHg,
             'eastward_wind': np.array([2, 0]) * units.knots,

tests/test_xarray.py

@@ -118,6 +118,13 @@ def test_convert_units(test_var):
     assert_almost_equal(test_var[0, 0, 0, 0], 18.44 * units.degC, 2)
 
 
+def test_convert_coordinate_units(test_ds_generic):
+    """Test conversion of coordinate units."""
+    result = test_ds_generic['test'].metpy.convert_coordinate_units('b', 'percent')
+    assert result['b'].data[1] == 100.
+    assert result['b'].metpy.units == units.percent
+
+
 def test_radian_projection_coords():
     """Test fallback code for radian units in projection coordinate variables."""
     proj = xr.DataArray(0, attrs={'grid_mapping_name': 'geostationary',
@@ -670,8 +677,8 @@ def test_coordinate_identification_shared_but_not_equal_coords():
 
 def test_check_no_quantification_of_xarray_data(test_ds_generic):
     """Test that .unit_array setter does not insert a `pint.Quantity` into the DataArray."""
-    var = test_ds_generic['e']
-    var.metpy.unit_array = [1000, 925, 850, 700, 500] * units.hPa
+    var = test_ds_generic['test']
+    var.metpy.unit_array = np.zeros(var.shape) * units.hPa
     assert not isinstance(var.data, units.Quantity)
 
 

tutorials/upperair_soundings.py

@@ -10,7 +10,7 @@
 problems. In this tutorial we will gather weather balloon data, plot it,
 perform a series of thermodynamic calculations, and summarize the results.
 To learn more about the Skew-T diagram and its use in weather analysis and
-forecasting, checkout `this <https://homes.comet.ucar.edu/~alanbol/aws-tr-79-006.pdf>`_
+forecasting, checkout `this <http://www.pmarshwx.com/research/manuals/AF_skewt_manual.pdf>`_
 air weather service guide.
 """