[我试图在Python OSMNX中使用based on this example遍历某些多边形，但是输出出现问题。
设置：
import geopandas as gpd
import matplotlib.pyplot as plt
import networkx as nx
import osmnx as ox
from descartes import PolygonPatch
from shapely.geometry import Point, LineString, Polygon
ox.config(log_console=True, use_cache=True)
ox.__version__
# get one color for each isochrone
iso_colours = ox.get_colors(n=len(trip_times), cmap='Reds', start=0.3, return_hex=True)
#info for later on
network_type = 'walk'
trip_times = [5, 10] #in minutes
travel_speed = 4.8 #walking speed in km/hour
metres_per_minute = travel_speed * 1000 / 60 #km per hour to m per minute
# isochrone function
def make_iso_polys(G, edge_buff=25, node_buff=50, infill=False):
isochrone_polys = []
for trip_time in sorted(trip_times, reverse=True):
subgraph = nx.ego_graph(G, centre_node, radius=trip_time, distance='time')
node_points = [Point((data['x'], data['y'])) for node, data in subgraph.nodes(data=True)]
nodes_gdf = gpd.GeoDataFrame({'id': subgraph.nodes()}, geometry=node_points)
nodes_gdf = nodes_gdf.set_index('id')
edge_lines = []
for n_fr, n_to in subgraph.edges():
f = nodes_gdf.loc[n_fr].geometry
t = nodes_gdf.loc[n_to].geometry
edge_lines.append(LineString([f,t]))
n = nodes_gdf.buffer(node_buff).geometry
e = gpd.GeoSeries(edge_lines).buffer(edge_buff).geometry
all_gs = list(n) + list(e)
new_iso = gpd.GeoSeries(all_gs).unary_union
# try to fill in surrounded areas so shapes will appear solid and blocks without white space inside them
if infill:
new_iso = Polygon(new_iso.exterior)
isochrone_polys.append(new_iso)
return isochrone_polys
# the area
mv = ox.graph_from_bbox(-37.705, -37.796, 144.949, 144.84, network_type='walk')
mv_projected = ox.project_graph(mv)
ox.plot_graph(mv_projected)
multiple_coords = ((-37.773981, 144.915669),
(-37.765443, 144.863070),
(-37.736089, 144.888972),
(-37.764914, 144.924148),
(-37.788513, 144.930533))
问题所在。我添加了一些其他文本来跟踪代码中发生的事情：
# test function to do multiple ones
def iterate_multiple_coords(the_coordinates):
for i in the_coordinates:
centre_node = ox.get_nearest_node(mv, (i[0], i[1]))
print("starting" + str(i)) # to check
# add an edge attribute for time in minutes required to traverse each edge
for u, v, k, data in mv_projected.edges(data=True, keys=True):
data['time'] = data['length'] / metres_per_minute
# make the polygons
isochrone_polys_iter = make_iso_polys(mv_projected, edge_buff=25, node_buff=0, infill=True)
print("done " + str([i])) # to check
poly_list.append(isochrone_polys_iter)
print("appended " + str([i])) # to check
return(poly_list)
#list of shapely objects
test = iterate_multiple_coords(multiple_coords)
这似乎可行，但是当您查看已创建的多边形时，它们只是其中两个的副本。它们应该都不同。
for i in test:
print(i[0].area)
print(i[1].area)
只需提供以下内容的副本：
[<shapely.geometry.polygon.Polygon object at 0x00000252EED81048>, <shapely.geometry.polygon.Polygon object at 0x0000025299DCD7B8>]
1221891.0262004482
278954.2285476034
[<shapely.geometry.polygon.Polygon object at 0x000002529A0FF978>, <shapely.geometry.polygon.Polygon object at 0x00000252F0884978>]
1170723.0839951886
254020.00263692273
我该如何解决？谢谢。
[尝试复制问题，我遇到两个错误。解决这些问题似乎可以产生正确的结果。首先，make_iso_polys也需要以centre_node作为参数：
def make_iso_polys(G, centre_node, edge_buff=25, node_buff=50, infill=False):
isochrone_polys = []
for trip_time in sorted(trip_times, reverse=True):
subgraph = nx.ego_graph(G, centre_node, radius=trip_time, distance='time')
node_points = [Point((data['x'], data['y'])) for node, data in subgraph.nodes(data=True)]
nodes_gdf = gpd.GeoDataFrame({'id': subgraph.nodes()}, geometry=node_points)
nodes_gdf = nodes_gdf.set_index('id')
edge_lines = []
for n_fr, n_to in subgraph.edges():
f = nodes_gdf.loc[n_fr].geometry
t = nodes_gdf.loc[n_to].geometry
edge_lines.append(LineString([f,t]))
n = nodes_gdf.buffer(node_buff).geometry
e = gpd.GeoSeries(edge_lines).buffer(edge_buff).geometry
all_gs = list(n) + list(e)
new_iso = gpd.GeoSeries(all_gs).unary_union
# try to fill in surrounded areas so shapes will appear solid and blocks without white space inside them
if infill:
new_iso = Polygon(new_iso.exterior)
isochrone_polys.append(new_iso)
return isochrone_polys
我怀疑那是您遇到的问题。如果您在某个时候在函数之外定义了centre_node，则make_iso_poly将在名称空间中进行搜索，直到找到一个值为止。
[我也遇到了一个错误，iterate_multiple_coords没有要附加的列表，很容易解决：
def iterate_multiple_coords(the_coordinates):
poly_list = []
for i in the_coordinates:
centre_node = ox.get_nearest_node(mv, (i[0], i[1]))
print("starting" + str(i)) # to check
# add an edge attribute for time in minutes required to traverse each edge
for u, v, k, data in mv_projected.edges(data=True, keys=True):
data['time'] = data['length'] / metres_per_minute
# make the polygons
isochrone_polys_iter = make_iso_polys(mv_projected,
centre_node,
edge_buff=25,
node_buff=0,
infill=True)
print("done " + str([i])) # to check
poly_list.append(isochrone_polys_iter)
print("appended " + str([i])) # to check
return(poly_list)
我尝试用更多的输出进行测试，以确保多边形不同：
#list of shapely objects
test = iterate_multiple_coords(multiple_coords)
for i, poly in enumerate(test):
print(i)
print(poly[0].bounds)
print(poly[0].area)
print(poly[1].bounds)
print(poly[1].area)
这给我回来
0
(315719.9722479802, -4183576.0970487385, 317146.7585685815, -4182104.248355794)
1064783.069852857
(316092.45915179665, -4183138.881268308, 316857.3685328224, -4182352.8318315353)
207488.55915115002
1
(311160.15906794026, -4182601.4787744572, 312318.75050440413, -4181146.474157421)
844021.6754682651
(311491.4241338904, -4182296.4498064136, 312171.21314883756, -4181535.6374544636)
181959.15194429446
2
(313349.77854383545, -4179191.5691777603, 314706.9086066517, -4177874.3106440073)
697618.2735243046
(313611.9777962584, -4178837.4315966303, 314316.9596420839, -4178365.0333478907)
105808.08447317046
3
(316506.3163716192, -4182533.536447418, 317712.9680439883, -4181044.336753285)
1042931.7802330595
(316764.0345564607, -4182162.9997046595, 317463.6017386513, -4181398.2886200016)
276870.23606513516
4
(317045.2449636515, -4185110.519037448, 318554.4721278832, -4183677.93438998)
1170827.5838636972
(317408.8052150706, -4184702.3494480574, 318143.3573653238, -4184063.5647333027)
253939.04383932063