Drawing a graph with NetworkX on a Basemap

Question

I want to plot a graph on a map where the nodes would be defined by coordinates (lat, long) and have some value associated.

I have been able to plot points as a scatterplot on a basemap but can't seem to find how to plot a graph on the map.

Thanks.

EDIT: I have added code on how I plotted the points on a basemap. Most of it has been adapted from code in this article.

from mpl_toolkits.basemap import Basemap
from shapely.geometry import Point, MultiPoint
import pandas as pd
import matplotlib.pyplot as plt

m = Basemap(
        projection='merc',
        ellps = 'WGS84',
        llcrnrlon=-130,
        llcrnrlat=25,
        urcrnrlon=-60,
        urcrnrlat=50,
        lat_ts=0,
        resolution='i',
        suppress_ticks=True)

# Create Point objects in map coordinates from dataframe lon
# and lat values
# I have a dataframe of coordinates
map_points = pd.Series(
                [Point(m(mapped_x, mapped_y)) 
                 for mapped_x, mapped_y in zip(df['lon'],
                                               df['lat'])])
amre_points = MultiPoint(list(map_points.values)) 

plt.clf()
fig = plt.figure()
ax = fig.add_subplot(111, axisbg='w', frame_on=False)
fig.set_size_inches(18.5, 10.5)

# Create a scatterplot on the map
dev = m.scatter(
            [geom.x for geom in map_points],
            [geom.y for geom in map_points],
            20, marker='o', lw=.25,
            facecolor='#33ccff', edgecolor='w',
            alpha=0.9,antialiased=True,
            zorder=3)

m.fillcontinents(color='#555555')

I get this image:

Answer 1

Here is one way to do it:

import networkx as nx
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap as Basemap
m = Basemap(
        projection='merc',
        llcrnrlon=-130,
        llcrnrlat=25,
        urcrnrlon=-60,
        urcrnrlat=50,
        lat_ts=0,
        resolution='i',
        suppress_ticks=True)

# position in decimal lat/lon
lats=[37.96,42.82]
lons=[-121.29,-73.95]
# convert lat and lon to map projection
mx,my=m(lons,lats)

# The NetworkX part
# put map projection coordinates in pos dictionary
G=nx.Graph()
G.add_edge('a','b')
pos={}
pos['a']=(mx[0],my[0])
pos['b']=(mx[1],my[1])
# draw
nx.draw_networkx(G,pos,node_size=200,node_color='blue')

# Now draw the map
m.drawcountries()
m.drawstates()
m.bluemarble()
plt.title('How to get from point a to point b')
plt.show()

Answer 2

As of today there is a nice alternative to basemap. Mplleaflet is a library inspired by mpld3. It plots faster than basemap, is more easy to use and allows to visualizing geographic data on beautiful interactive openstreetmap. The input can be longitude and latitude the library automatically projects the data properly.

Input dictionary pos, where the node (country) is the key and long lat are saved as value.

 pos = {u'Afghanistan': [66.00473365578554, 33.83523072784668],
 u'Aland': [19.944009818523348, 60.23133494165451],
 u'Albania': [20.04983396108883, 41.14244989474517],
 u'Algeria': [2.617323009197829, 28.158938494487625],
 .....

Plotting is as easy as:

import mplleaflet

fig, ax = plt.subplots()

nx.draw_networkx_nodes(GG,pos=pos,node_size=10,node_color='red',edge_color='k',alpha=.5, with_labels=True)
nx.draw_networkx_edges(GG,pos=pos,edge_color='gray', alpha=.1)
nx.draw_networkx_labels(GG,pos, label_pos =10.3)

mplleaflet.display(fig=ax.figure)