How to change the font size of the color bar of a GeoPandas choropleth plot

Question

When I try to use the legend_kwds argument to change the font size of my colorbar, I keep getting this error

TypeError: init() got an unexpected keyword argument 'fontsize'

ax = df.plot(figsize=(20,16), alpha=0.8, column='value', legend=True, cmap='OrRd', legend_kwds={'fontsize':20})
    
plt.show()

Does anyone know how I can increase the font size of the colorbar with GeoPandas? I can't seem to find a keyword that works. I'm using GeoPandas 0.8.1 and Matplotlib 3.3.1.

Answer 1

You can use matplotlib workaround rather than passing all the complicate parameters in a single statement geopandas' plot function does.

import numpy as np
import geopandas as gpd
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable

# for demo purposes, use the builtin data
world = gpd.read_file(gpd.datasets.get_path('naturalearth_lowres'))
africa = world[world.continent=='Africa']
maxv, minv = max(africa.pop_est), min(africa.pop_est)

fig, ax = plt.subplots(figsize=(7,6))
divider = make_axes_locatable(ax)

# create `cax` for the colorbar
cax = divider.append_axes("right", size="5%", pad=0.1)

# plot the geodataframe specifying the axes `ax` and `cax` 
africa.plot(column="pop_est", cmap='magma', legend=True, \
            vmin=minv, vmax=maxv, ax=ax, cax=cax)

# manipulate the colorbar `cax`
cax.set_ylabel('pop_est', rotation=90)
# set `fontsize` on the colorbar `cax`
cax.set_yticklabels(np.linspace(minv, maxv, 10, dtype=np.dtype(np.uint64)), {'fontsize': 8})

plt.show()

The output plot:

Answer 2

I encountered the same problem, and I found that the answer does not work correctly - the labels on the legend are actually wrong.

So using the same idea, you can call

cax.tick_params(labelsize='20')

this will keep the default ticks that the plot creates, but you can change the details.