Merge pull request Unidata#927 from jrleeman/county_features

Add US County features

examples/plots/US_Counties.py

@@ -0,0 +1,26 @@
+# Copyright (c) 2018 MetPy Developers.
+# Distributed under the terms of the BSD 3-Clause License.
+# SPDX-License-Identifier: BSD-3-Clause
+"""
+US Counties
+===========
+
+Demonstrate how to plot US counties at all three available resolutions.
+"""
+import cartopy.crs as ccrs
+import matplotlib.pyplot as plt
+
+from metpy.plots import USCOUNTIES
+
+###########################################
+
+proj = ccrs.LambertConformal(central_longitude=-85.0, central_latitude=45.0)
+
+fig = plt.figure(figsize=(12, 9))
+ax1 = fig.add_subplot(1, 3, 1, projection=proj)
+ax2 = fig.add_subplot(1, 3, 2, projection=proj)
+ax3 = fig.add_subplot(1, 3, 3, projection=proj)
+
+for scale, axis in zip(['20m', '5m', '500k'], [ax1, ax2, ax3]):
+    axis.set_extent([270.25, 270.9, 38.15, 38.75], ccrs.Geodetic())
+    axis.add_feature(USCOUNTIES.with_scale(scale), edgecolor='black')

metpy/calc/cross_sections.py

@@ -7,7 +7,6 @@
 is based around xarray DataArrays.
 """
 
-import cartopy.crs as ccrs
 import numpy as np
 import xarray as xr
 
@@ -85,6 +84,7 @@ def latitude_from_cross_section(cross):
     if CFConventionHandler.check_axis(y, 'lat'):
         return y
     else:
+        import cartopy.crs as ccrs
         latitude = ccrs.Geodetic().transform_points(cross.metpy.cartopy_crs,
                                                     cross.metpy.x.values,
                                                     y.values)[..., 1]

metpy/interpolate/slices.py

@@ -3,7 +3,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 """Tools for interpolating to a vertical slice/cross section through data."""
 
-import cartopy.crs as ccrs
 import numpy as np
 import xarray as xr
 
@@ -81,6 +80,7 @@ def geodesic(crs, start, end, steps):
     cross_section
 
     """
+    import cartopy.crs as ccrs
     from pyproj import Geod
 
     # Geod.npts only gives points *in between* the start and end, and we want to include

metpy/plots/__init__.py

@@ -3,6 +3,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 r"""Contains functionality for making meteorological plots."""
 
+import logging
+
 # Trigger matplotlib wrappers
 from . import _mpl  # noqa: F401
 from ._util import add_metpy_logo, add_timestamp, add_unidata_logo, convert_gempak_color
@@ -11,9 +13,16 @@
 from .station_plot import *  # noqa: F403
 from .wx_symbols import *  # noqa: F403
 
+logger = logging.getLogger(__name__)
+
 __all__ = ctables.__all__[:]  # pylint: disable=undefined-variable
 __all__.extend(skewt.__all__)  # pylint: disable=undefined-variable
 __all__.extend(station_plot.__all__)  # pylint: disable=undefined-variable
 __all__.extend(wx_symbols.__all__)  # pylint: disable=undefined-variable
-__all__.extend([add_metpy_logo, add_timestamp, convert_gempak_color,
-                add_unidata_logo])  # pylint: disable=undefined-variable
+__all__.extend([add_metpy_logo, add_timestamp, add_unidata_logo,
+                convert_gempak_color])  # pylint: disable=undefined-variable
+try:
+    from .cartopy_utils import USCOUNTIES
+    __all__.extend([USCOUNTIES])
+except ImportError:
+    logger.warning('Cannot import USCOUNTIES without cartopy installed.')

metpy/plots/cartopy_utils.py

@@ -0,0 +1,43 @@
+# Copyright (c) 2018 MetPy Developers.
+# Distributed under the terms of the BSD 3-Clause License.
+# SPDX-License-Identifier: BSD-3-Clause
+"""Cartopy specific mapping utilities."""
+
+import cartopy.feature as cfeat
+import cartopy.io.shapereader as shpreader
+
+from ..cbook import get_test_data
+
+
+class USCountiesFeature(cfeat.NaturalEarthFeature):
+    """A simple interface to US County shapefiles."""
+
+    def __init__(self, scale, **kwargs):
+        """Create USCountiesFeature instance."""
+        super(USCountiesFeature, self).__init__('', 'us_counties', scale, **kwargs)
+
+    def geometries(self):
+        """Return an iterator of (shapely) geometries for this feature."""
+        # Ensure that the associated files are in the cache
+        fname = 'us_counties_{}'.format(self.scale)
+        for extension in ['.dbf', '.shx']:
+            get_test_data(fname + extension)
+        path = get_test_data(fname + '.shp', as_file_obj=False)
+        return iter(tuple(shpreader.Reader(path).geometries()))
+
+    def with_scale(self, new_scale):
+        """
+        Return a copy of the feature with a new scale.
+
+        Parameters
+        ----------
+        new_scale
+            The new dataset scale, i.e. one of '500k', '5m', or '20m'.
+            Corresponding to 1:500,000, 1:5,000,000, and 1:20,000,000
+            respectively.
+
+        """
+        return USCountiesFeature(new_scale, **self.kwargs)
+
+
+USCOUNTIES = USCountiesFeature('20m', facecolor='None')

metpy/plots/tests/test_cartopy_utils.py

@@ -0,0 +1,43 @@
+# Copyright (c) 2018 MetPy Developers.
+# Distributed under the terms of the BSD 3-Clause License.
+# SPDX-License-Identifier: BSD-3-Clause
+"""Test the cartopy utilities."""
+
+import cartopy.crs as ccrs
+import matplotlib
+import matplotlib.pyplot as plt
+import pytest
+
+from metpy.plots import USCOUNTIES
+# Fixtures to make sure we have the right backend and consistent round
+from metpy.testing import patch_round, set_agg_backend  # noqa: F401, I202
+
+MPL_VERSION = matplotlib.__version__[:3]
+
+
+@pytest.mark.mpl_image_compare(tolerance=0.053, remove_text=True)
+def test_us_county_defaults():
+    """Test the default US county plotting."""
+    proj = ccrs.LambertConformal(central_longitude=-85.0, central_latitude=45.0)
+
+    fig = plt.figure(figsize=(12, 9))
+    ax = fig.add_subplot(1, 1, 1, projection=proj)
+    ax.set_extent([270.25, 270.9, 38.15, 38.75], ccrs.Geodetic())
+    ax.add_feature(USCOUNTIES, edgecolor='black')
+    return fig
+
+
+@pytest.mark.mpl_image_compare(tolerance=0.092, remove_text=True)
+def test_us_county_scales():
+    """Test US county plotting with all scales."""
+    proj = ccrs.LambertConformal(central_longitude=-85.0, central_latitude=45.0)
+
+    fig = plt.figure(figsize=(12, 9))
+    ax1 = fig.add_subplot(1, 3, 1, projection=proj)
+    ax2 = fig.add_subplot(1, 3, 2, projection=proj)
+    ax3 = fig.add_subplot(1, 3, 3, projection=proj)
+
+    for scale, axis in zip(['20m', '5m', '500k'], [ax1, ax2, ax3]):
+        axis.set_extent([270.25, 270.9, 38.15, 38.75], ccrs.Geodetic())
+        axis.add_feature(USCOUNTIES.with_scale(scale), edgecolor='black')
+    return fig

metpy/static-data-manifest.txt

@@ -144,7 +144,13 @@ nov11_sounding.txt 6fa3e0920314a7d55d6e1020eb934e18d9623c5fb1a40aaad546a25ed225e
 rbf_test.npz f035f4415ea9bf04dcaf8affd7748f6519638655dcce90dad2b54fe0032bf32d
 station_data.txt 3c1b71abb95ef8fe4adf57e47e2ce67f3529c6fe025b546dd40c862999fc5ffe
 timeseries.csv 2d79f8f21ad1fcec12d0e24750d0958631e92c9148adfbd1b7dc8defe8c56fc5
+us_counties_20m.dbf b5eeaa4769f25324d52933a6067e9a90315a77fefcdbefd0c7d99e94fd0cbb41
 us_counties_20m.shp 8acb8bfbcf670028f7ce6c1c11ae08b21844b1c882c26ef397df33231831dee9
+us_counties_20m.shx 131ccb63c365415c81c4fcd686b2bcbb9166e3a3d1fe97c1a5fc28344036a4ae
+us_counties_500k.dbf 8cb3e42c3d951cf5b15e395bee61eb1ad50c0470bd0937e7288526605bf1ab85
 us_counties_500k.shp 06463cf329d6f412d7f3323748225aca1ca495a8c04af58cfaf169fc3a8c8df4
+us_counties_500k.shx aa301ee507e17bcd84a0792648eaea17a5efd7b274d14689a285603c0a61a8ba
+us_counties_5m.dbf f7e5b7cb1da1a306652b4ca94212a91b4e08006691366ede1bca57c1b31018a4
 us_counties_5m.shp be255ca37625e5feef7808ef996e803c6412ee67e52c29ee0b603b569eba083c
+us_counties_5m.shx 7412c519095b9d2c3d3bf0e681f784f2b44fb4b4b6ce58d5b60fcd740dab2895
 wrf_example.nc dcc1444db327507730334fd94dcb223025f77791448dd394f3ba06391ddbf98f