Circular Barplot in Python with matplotlib (Polar Bar Chart)

A circular barplot is a bar chart drawn on polar coordinates: each bar is placed at an angle and its length is the value. It is visually striking and works well with cyclic data, like the months of the year. The examples show the monthly hours of sunshine of a city.

Bars on polar axes

Create polar axes with subplot_kw = {"projection": "polar"} and draw the bars with bar, using the angles as X values.

import numpy as np
import matplotlib.pyplot as plt

months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
sunshine = np.array([150, 160, 210, 230, 280, 320, 350, 330, 260, 200, 150, 140])
angles = np.linspace(0, 2 * np.pi, len(months), endpoint = False)

fig, ax = plt.subplots(subplot_kw = {"projection": "polar"})
ax.bar(angles, sunshine, width = 0.45)
ax.set_xticks(angles, months)
# plt.show()

Circular barplot in matplotlib

Hole in the center and orientation

Set a negative lower limit on the radial axis to leave a hole in the center. set_theta_zero_location and set_theta_direction make the first bar start at the top and go clockwise, like a clock.

import numpy as np
import matplotlib.pyplot as plt

months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
sunshine = np.array([150, 160, 210, 230, 280, 320, 350, 330, 260, 200, 150, 140])
angles = np.linspace(0, 2 * np.pi, len(months), endpoint = False)

fig, ax = plt.subplots(subplot_kw = {"projection": "polar"})
ax.bar(angles, sunshine, width = 0.45)

ax.set_ylim(-150, 360)
ax.set_theta_zero_location("N")
ax.set_theta_direction(-1)
ax.set_xticks(angles, months)
ax.set_yticks([])
# plt.show()

Circular barplot with a hole in the center in matplotlib

Color by value

Map the values to a colormap to color each bar and remove the grid and the frame for a cleaner look.

import numpy as np
import matplotlib.pyplot as plt

months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
sunshine = np.array([150, 160, 210, 230, 280, 320, 350, 330, 260, 200, 150, 140])
angles = np.linspace(0, 2 * np.pi, len(months), endpoint = False)

colors = plt.cm.YlOrRd(sunshine / sunshine.max())

fig, ax = plt.subplots(subplot_kw = {"projection": "polar"})
ax.bar(angles, sunshine, width = 0.5, color = colors, edgecolor = "white")
ax.set_ylim(-150, 360)
ax.set_theta_zero_location("N")
ax.set_theta_direction(-1)
ax.set_xticks(angles, months)
ax.set_yticks([])
ax.spines["polar"].set_visible(False)
# plt.show()

Circular barplot colored by value in matplotlib

Values as labels

Write the value of each bar at its end with text, using the angle of the bar as X coordinate and the value plus a small margin as Y coordinate.

import numpy as np
import matplotlib.pyplot as plt

months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
sunshine = np.array([150, 160, 210, 230, 280, 320, 350, 330, 260, 200, 150, 140])
angles = np.linspace(0, 2 * np.pi, len(months), endpoint = False)

fig, ax = plt.subplots(subplot_kw = {"projection": "polar"})
ax.bar(angles, sunshine, width = 0.45, color = "#F4A261")
ax.set_ylim(-150, 400)
ax.set_theta_zero_location("N")
ax.set_theta_direction(-1)
ax.set_xticks(angles, months)
ax.set_yticks([])

for angle, value in zip(angles, sunshine):
    ax.text(angle, value + 30, str(value), ha = "center", fontsize = 8)
# plt.show()

Circular barplot with value labels in matplotlib