pythonmatplotlibgeopandaspysal

format/round numerical legend label in GeoPandas


I'm looking for a way to format/round the numerical legend labels in those maps produced by .plot() function in GeoPandas. For example:

gdf.plot(column='pop2010', scheme='QUANTILES', k=4)

This gives me a legend with many decimal places:

enter image description here

I want the legend label to be integers.


Solution

  • As I recently encountered the same issue, and a solution does not appear to be readily available on Stack Overflow or other sites, I thought I would post the approach I took in case it is useful.

    First, a basic plot using the geopandas world map:

    # load world data set    
    world_orig = geopandas.read_file(geopandas.datasets.get_path('naturalearth_lowres'))
    world = world_orig[(world_orig['pop_est'] > 0) & (world_orig['name'] != "Antarctica")].copy()
    world['gdp_per_cap'] = world['gdp_md_est'] / world['pop_est']
    
    # basic plot
    fig = world.plot(column='pop_est', figsize=(12,8), scheme='fisher_jenks', 
                     cmap='YlGnBu', legend=True)
    leg = fig.get_legend()
    leg._loc = 3
    plt.show()
    

    world map v1

    The method I used relied on the get_texts() method for the matplotlib.legend.Legend object, then iterating over the items in leg.get_texts(), splitting the text element into the lower and upper bounds, and then creating a new string with formatting applied and setting this with the set_text() method.

    # formatted legend
    fig = world.plot(column='pop_est', figsize=(12,8), scheme='fisher_jenks', 
                     cmap='YlGnBu', legend=True)
    leg = fig.get_legend()
    leg._loc = 3
    
    for lbl in leg.get_texts():
        label_text = lbl.get_text()
        lower = label_text.split()[0]
        upper = label_text.split()[2]
        new_text = f'{float(lower):,.0f} - {float(upper):,.0f}'
        lbl.set_text(new_text)
    
    plt.show()
    

    This is very much a 'trial and error' approach, so I wouldn't be surprised if there were a better way. Still, perhaps this will be helpful.

    world map v2