Geopandas Plotting & Legends Symbology - QUESTION

Hi All. I have a question about how plots and legends work with geopandas. I set the colors and line symbology using a list. And i used .plot() to plot the data

Here is a plot that i made of roads using the cropped natural earth data:

# plotting using geopandas
road_colors = ['black', 'grey', 'grey', 'black', 'grey', 'grey' ]
line_widths = [1, .5, .5, 1, .5,.5]
# plot the data
fig, ax = plt.subplots(figsize  = (12, 8))
country_boundary_us.plot(alpha = 1, color="white", 
                         edgecolor = "black", 
                         ax = ax)
us_roads_only.plot(ax=ax, column='type', 
                   cmap = ListedColormap(road_colors), 
                   linewidth = line_widths,
                   legend = True)
ax.set_axis_off()
plt.axis('equal');

Notice that my legend shows the road symbols as circles. Yet i’d prefer lines.

Here – i try to create a nicer legend using ax.legend().

# make it a bit nicer using a dictionary to assign colors and line widths
road_attrs = {'Beltway': ['black',2], 
               'Secondary Highway': ['grey',.5],
               'Road': ['grey',.5],
               'Bypass': ['grey', .5], 
               'Ferry Route': ['grey', .5], 
               'Major Highway': ['black', 1]}

# plot the data
fig, ax = plt.subplots(figsize  = (12, 8))

for ctype, data in us_roads_only.groupby('type'):
    data.plot(color=road_attrs[ctype][0], 
              label = ctype,
              ax = ax, 
              linewidth=road_attrs[ctype][1])

country_boundary_us.plot(alpha = 1, color="white", edgecolor = "black", ax = ax)
ax.legend(title="legend")
ax.set_title("United States Roads by Type", fontsize=25)
ax.set_axis_off()
plt.axis('equal');

I may be missing something. But can geopandas create a legend using the unique symbology applied to each (group) like ax.legend() can do natively if there is a label object? Or can you kindly help me understand how i would customize a legend created by geopandas? Perhaps my approach is wrong.

My GOAL: i’m trying to figure out the best way to teach students how to create a map with a legend in python.

Many thanks for any guidance.

[lwasser]

HAHAHA got it @martinfleis 😃 with COVID and the cold evenings on the horizon perhaps i will find some time to have a look at plotting.py 😃 it’s been on my mind for a while. Thank you!

[lwasser]

thanks @jdmcbr ok that makes sense. I had a look at the code and suspected that was the case but i wasn’t fully certain. it would be a very nice feature to have. The matplotlib legend functionality is actually quite nice so it does seem as if geopandas could take advantage of that potentially. I appreciate your response!