Rework naturalearth example using geopandas (#24).

examples/cartography/plot_naturalearth_geopandas.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+# Copyright (c) 2022, Julien Seguinot (juseg.github.io)
+# GNU General Public License v3.0+ (https://www.gnu.org/licenses/gpl-3.0.txt)
+
+"""
+Natural Earth and GeoPandas
+===========================
+
+Demonstrate use of GeoPandas to highlight particular Natural Earth features.
+"""
+
+import matplotlib.pyplot as plt
+import hyoga.open
+import hyoga.plot
+
+
+# initialize figure
+ax = plt.subplot()
+
+# plot demo bedrock altitude
+with hyoga.open.example('pism.alps.out.2d.nc') as ds:
+    ds.hyoga.plot.bedrock_altitude(ax=ax, vmin=0, vmax=4500)
+
+    # plot canonical Natural Earth background
+    ds.hyoga.plot.naturalearth(ax=ax)
+
+    # get dataset crs, we need this
+    crs = ds.proj4
+
+# lock axes extent
+ax.set_autoscale_on(False)
+
+# plot the Po river and Lago di Garda in blue
+rivers = hyoga.open.naturalearth('rivers_lake_centerlines')
+rivers[rivers.name == 'Po'].to_crs(crs).plot(ax=ax, edgecolor='tab:blue')
+lakes = hyoga.open.naturalearth('lakes')
+lakes[lakes.name == 'Lago di Garda'].to_crs(crs).plot(ax=ax)
+
+# plot the outline of Switzerland in red
+countries = hyoga.open.naturalearth('admin_0_countries', category='cultural')
+countries[countries.NAME == 'Switzerland'].to_crs(crs).plot(
+    ax=ax, edgecolor='tab:red', facecolor='none', linewidth=2)
+
+# plot Austria's Salzburg state in green
+states = hyoga.open.naturalearth(
+    'admin_1_states_provinces', category='cultural')
+states[states.name == 'Salzburg'].to_crs(crs).plot(
+    ax=ax, alpha=0.75, facecolor='tab:green')
+
+# set axes properties
+ax.set_title('Natural Earth with Geopandas')
+ax.xaxis.set_visible(False)
+ax.yaxis.set_visible(False)
+
+# show
+plt.show()