Matplotlib pie charts as scatter plot

Question

I have an interesting problem where I am trying to use multiple matplotlib pie charts as a scatter plot. I have read this post regarding this matplotlib tutorial and was able to get those working. However, I found that I was able to achieve the same results using the built-in pie function and plotting many pie charts on the same axis.

When using this alternative method, I found that after plotting the pie charts the axes lose their labels and whenever you pan the original data is still contained inside of the where the bounds of the original data should be, but the pie charts are only contained inside of the figure canvas.

The following code replicates the issue that I'm having.

import matplotlib.pyplot as plt
import pandas as pd
import random

def rand(): #simulate some random data
    return [random.randint(0,100) for _ in range(10)]

def plot_pie(x, ax): 
    ax.pie(x[['a','b','c']], center=(x['lat'],x['lon']), radius=1,colors=['r', 'b', 'g'])

#my data is stored in a similar styled dataframe that I read from a csv and the data is static
sim_data = pd.DataFrame({'a':rand(),'b':rand(),'c':rand(), 'lat':rand(),'lon':rand()})

fig, ax = plt.subplots()
plt.scatter(x=sim_data['lat'], y=sim_data['lon'], s=1000, facecolor='none',edgecolors='r')
y_init = ax.get_ylim()
x_init = ax.get_xlim()

sim_data.apply(lambda x : plot_pie(x,ax), axis=1)
ax.set_ylim(y_init)
ax.set_xlim(x_init)
plt.show()

The reason that I reset the x and y limits of the axis is that I assume the pie function automatically sets the bounds of the axes to the last pie chart and this was my work around.

UPDATE

After reading the docs again I found that matplotlib pie chart objects as a default are set to not clip to the extents of any axes. To solve it, just updating that parameter seemed to work for me. The following code is the solution to my problem. I also found that by plotting each pie chart I would lose my axes ticks, to solve that I had to pass the frame parameter to the pie charts.

def plot_pie(x, ax):
    ax.pie(x[['a','b','c']], center=(x['lat'],x['lon']), radius=1,colors=['r', 'b', 'g'], wedgeprops={'clip_on':True}, frame=True)

user_7599215 · Answer

Data generated as in original post. I added a frame for each plot for clarity.

def plot_pie(x, ax, r=1): 
    # radius for pieplot size on a scatterplot
    ax.pie(x[['a','b','c']], center=(x['lat'],x['lon']), radius=r, colors=['r', 'b', 'g'])

    
fig, axs = plt.subplots(1, 3, figsize=(15, 5))
fig.patch.set_facecolor('white')

# original plot
ax = axs[0]
ax.scatter(x=sim_data['lat'], y=sim_data['lon'], s=1000, facecolor='none', edgecolors='r')
y_init = ax.get_ylim()
x_init = ax.get_xlim()
sim_data.apply(lambda x : plot_pie(x,ax), axis=1)
ax.set_ylim(y_init)
ax.set_xlim(x_init)
ax.set_title('Original')
ax.set_frame_on(True)

# r-beginner's solution
ax = axs[1]
ax.scatter(x=sim_data['lat'], y=sim_data['lon'], s=1000, facecolor='none', edgecolors='r')
y_init = ax.get_ylim()
x_init = ax.get_xlim()
sim_data.apply(lambda x : plot_pie(x,ax), axis=1)
ax.set_ylim([0, y_init[1]*1.1])
ax.set_xlim([0, x_init[1]*1.1])
ax.set_title('r-beginners')
ax.set_frame_on(True)

# my solution
ax = axs[2]
# do not use `s=` for size, it will not work properly when you are scattering pieplots
# because pieplots will be plotted above them
ax.scatter(x=sim_data['lat'], y=sim_data['lon'], s=0)
# git min/max values for the axes
y_init = ax.get_ylim()
x_init = ax.get_xlim()
sim_data.apply(lambda x : plot_pie(x, ax, r=7), axis=1)
# from zero to xlim/ylim with step 10
_ = ax.yaxis.set_ticks(range(0, round(y_init[1])+10, 10))
_ = ax.xaxis.set_ticks(range(0, round(x_init[1])+10, 10))
_ = ax.set_title('My')
ax.set_frame_on(True)

Matplotlib pie charts as scatter plot

1 Answers