add OSMnx example (#4383)

1 files changed, 39 insertions, 7 deletions

diff --git a/examples/geospatial/plot_osmnx.py b/examples/geospatial/plot_osmnx.py
index 1fedc352..86a51445 100644
--- a/examples/geospatial/plot_osmnx.py
+++ b/examples/geospatial/plot_osmnx.py
@@ -3,15 +3,47 @@
 OSMnx
 =====
 
-This example shows how to read a shapefile with OSMnx
-and convert it to a NetworkX graph....
+This example shows how to use OSMnx to download and model a street network
+from OpenStreetMap, visualize centrality, and save the graph as a shapefile,
+a GeoPackage, or GraphML.
+
+OSMnx is a Python package to retrieve, model, analyze, and visualize
+OpenStreetMap street networks as NetworkX MultiDiGraph objects. It can also
+retrieve any other spatial data from OSM as geopandas GeoDataFrames. See
+https://osmnx.readthedocs.io/ for OSMnx documentation and usage.
 """
 
-import osmnx as ox
 import networkx as nx
+import osmnx as ox
+
+ox.config(use_cache=True, log_console=True)
+
+# download street network data from OSM and construct a MultiDiGraph model
+G = ox.graph_from_point((37.79, -122.41), dist=750, network_type="drive")
+
+# impute edge (driving) speeds and calculate edge traversal times
+G = ox.add_edge_speeds(G)
+G = ox.add_edge_travel_times(G)
+
+# you can convert MultiDiGraph to/from geopandas GeoDataFrames
+gdf_nodes, gdf_edges = ox.graph_to_gdfs(G)
+G = ox.graph_from_gdfs(gdf_nodes, gdf_edges, graph_attrs=G.graph)
+
+# convert MultiDiGraph to DiGraph to use nx.betweenness_centrality function
+# choose between parallel edges by minimizing travel_time attribute value
+D = ox.utils_graph.get_digraph(G, weight="travel_time")
+
+# calculate node betweenness centrality, weighted by travel time
+bc = nx.betweenness_centrality(D, weight="travel_time", normalized=True)
+nx.set_node_attributes(G, values=bc, name="bc")
 
-# %%
-# TODO
+# plot the graph, coloring nodes by betweenness centrality
+nc = ox.plot.get_node_colors_by_attr(G, "bc", cmap="plasma")
+fig, ax = ox.plot_graph(
+    G, bgcolor="k", node_color=nc, node_size=50, edge_linewidth=2, edge_color="#333333"
+)
 
-G = ox.graph_from_point((37.79, -122.41), dist=750, network_type="all")
-ox.plot_graph(G)
+# save graph to shapefile, geopackage, or graphml
+ox.save_graph_shapefile(G, filepath="./graph_shapefile/")
+ox.save_graph_geopackage(G, filepath="./graph.gpkg")
+ox.save_graphml(G, filepath="./graph.graphml")