[GIS] Python Mapping in Matplotlib Cartopy Color One Country

Question

I have plotted a map of the world using matplotlib Cartopy. Now I want to select a specific country in the map in this case the United States and change the color. I think this is possible but not sure? I also, don't know how to filter the data for a 'country name' or other data that might be contained in the file.

import matplotlib.pyplot as plt
import cartopy
ax = plt.axes(projection=cartopy.crs.PlateCarree())
ax.add_feature(cartopy.feature.LAND)
ax.add_feature(cartopy.feature.OCEAN)
ax.add_feature(cartopy.feature.COASTLINE)
ax.add_feature(cartopy.feature.BORDERS, linestyle='-', alpha=.5)
ax.add_feature(cartopy.feature.LAKES, alpha=0.95)
#ax.add_feature(cartopy.feature.RIVERS)
ax.set_extent([-150, 60, -25, 60])

All I want is two colors one for the United States and one color for all other countries.
Thanks for the help since I'm new to mapping via python.

Answer 1

You have to use the cartopy shapereader and play a bit with records and geometries:

import matplotlib.pyplot as plt
import cartopy
import cartopy.io.shapereader as shpreader
import cartopy.crs as ccrs

ax = plt.axes(projection=ccrs.PlateCarree())
#ax.add_feature(cartopy.feature.LAND)
ax.add_feature(cartopy.feature.OCEAN)
#ax.add_feature(cartopy.feature.COASTLINE)
#ax.add_feature(cartopy.feature.BORDERS, linestyle='-', alpha=.5)
#ax.add_feature(cartopy.feature.LAKES, alpha=0.95)
#ax.add_feature(cartopy.feature.RIVERS)
ax.set_extent([-150, 60, -25, 60])

shpfilename = shpreader.natural_earth(resolution='110m',
                                      category='cultural',
                                      name='admin_0_countries')
reader = shpreader.Reader(shpfilename)
countries = reader.records()

for country in countries:
    if country.attributes['adm0_a3'] == 'USA':
        ax.add_geometries(country.geometry, ccrs.PlateCarree(),
                          facecolor=(0, 0, 1),
                          label=country.attributes['adm0_a3'])
    else:
        ax.add_geometries(country.geometry, ccrs.PlateCarree(),
                          facecolor=(0, 1, 0),
                          label=country.attributes['adm0_a3'])

plt.show()

Note: the facecolors are the RGB values divided by 255.