78 of 100: Circle area chart in matplotlib
At the beginning of the year I challenged myself to create all 100 visualizations using python and matplotlib from the 1 dataset,100 visualizations project and I am sharing with you the code for all the visualizations.
Note: Data Viz Project is copyright Ferdio and available under a Creative Commons Attribution – Non Commercial – No Derivatives 4.0 International license. I asked Ferdio and they told me they used a Design tool to create all the plots.
Collaborate
There are a ton of improvements that can be made on the code, so let me know in the comments any improvements you make and I will update the post accordingly!
This is the original viz that we are trying to recreate in matplotlib:

Import the packages
We will need the following packages:
import matplotlib.pyplot as plt
from matplotlib.lines import Line2D
import numpy as np
import pandas as pd
Generate the data
We could actually go from numpy to matplotlib, but most data projects use pandas to transform the data, so I am using a pandas dataframe as the starting point.
data = {
"year": [2004, 2022, 2004, 2022, 2004, 2022],
"countries" : [ "Denmark", "Denmark", "Norway", "Norway","Sweden", "Sweden",],
"sites": [4,10,5,8,13,15]
}
df= pd.DataFrame(data)
index | year | countries | sites |
---|---|---|---|
0 | 2004 | Sweden | 13 |
1 | 2022 | Sweden | 15 |
2 | 2004 | Denmark | 4 |
3 | 2022 | Denmark | 10 |
4 | 2004 | Norway | 5 |
5 | 2022 | Norway | 8 |
We need to create the subtotals for each year, the colors and then sort the data.
df = df.sort_values(['countries' ,'year' ], ascending=True ).reset_index(drop=True)
df['sub_total'] = df.groupby('year')['sites'].transform('sum')
df['colors'] = ["#CC5A43","#CC5A43","#2C324F","#2C324F","#5375D4","#5375D4"]
Plot the chart
class BubbleChart:
def __init__(self, area, bubble_spacing=0):
"""
Setup for bubble collapse.
Parameters
----------
area : array-like
Area of the bubbles.
bubble_spacing : float, default: 0
Minimal spacing between bubbles after collapsing.
Notes
-----
If "area" is sorted, the results might look weird.
"""
area = np.asarray(area)
r = np.sqrt(area / np.pi)
self.bubble_spacing = bubble_spacing
self.bubbles = np.ones((len(area), 4))
self.bubbles[:, 2] = r
self.bubbles[:, 3] = area
self.maxstep = 2 * self.bubbles[:, 2].max() + self.bubble_spacing
self.step_dist = self.maxstep / 2
# calculate initial grid layout for bubbles
length = np.ceil(np.sqrt(len(self.bubbles)))
grid = np.arange(length) * self.maxstep
gx, gy = np.meshgrid(grid, grid)
self.bubbles[:, 0] = gx.flatten()[:len(self.bubbles)]
self.bubbles[:, 1] = gy.flatten()[:len(self.bubbles)]
self.com = self.center_of_mass()
def center_of_mass(self):
return np.average(
self.bubbles[:, :2], axis=0, weights=self.bubbles[:, 3]
)
def center_distance(self, bubble, bubbles):
return np.hypot(bubble[0] - bubbles[:, 0],
bubble[1] - bubbles[:, 1])
def outline_distance(self, bubble, bubbles):
center_distance = self.center_distance(bubble, bubbles)
return center_distance - bubble[2] - \
bubbles[:, 2] - self.bubble_spacing
def check_collisions(self, bubble, bubbles):
distance = self.outline_distance(bubble, bubbles)
return len(distance[distance < 0])
def collides_with(self, bubble, bubbles):
distance = self.outline_distance(bubble, bubbles)
return np.argmin(distance, keepdims=True)
def collapse(self, n_iterations=50):
"""
Move bubbles to the center of mass.
Parameters
----------
n_iterations : int, default: 50
Number of moves to perform.
"""
for _i in range(n_iterations):
moves = 0
for i in range(len(self.bubbles)):
rest_bub = np.delete(self.bubbles, i, 0)
# try to move directly towards the center of mass
# direction vector from bubble to the center of mass
dir_vec = self.com - self.bubbles[i, :2]
# shorten direction vector to have length of 1
dir_vec = dir_vec / np.sqrt(dir_vec.dot(dir_vec))
# calculate new bubble position
new_point = self.bubbles[i, :2] + dir_vec * self.step_dist
new_bubble = np.append(new_point, self.bubbles[i, 2:4])
# check whether new bubble collides with other bubbles
if not self.check_collisions(new_bubble, rest_bub):
self.bubbles[i, :] = new_bubble
self.com = self.center_of_mass()
moves += 1
else:
# try to move around a bubble that you collide with
# find colliding bubble
for colliding in self.collides_with(new_bubble, rest_bub):
# calculate direction vector
dir_vec = rest_bub[colliding, :2] - self.bubbles[i, :2]
dir_vec = dir_vec / np.sqrt(dir_vec.dot(dir_vec))
# calculate orthogonal vector
orth = np.array([dir_vec[1], -dir_vec[0]])
# test which direction to go
new_point1 = (self.bubbles[i, :2] + orth *
self.step_dist)
new_point2 = (self.bubbles[i, :2] - orth *
self.step_dist)
dist1 = self.center_distance(
self.com, np.array([new_point1]))
dist2 = self.center_distance(
self.com, np.array([new_point2]))
new_point = new_point1 if dist1 < dist2 else new_point2
new_bubble = np.append(new_point, self.bubbles[i, 2:4])
if not self.check_collisions(new_bubble, rest_bub):
self.bubbles[i, :] = new_bubble
self.com = self.center_of_mass()
if moves / len(self.bubbles) < 0.1:
self.step_dist = self.step_dist / 2
def plot(self, ax, labels, colors):
"""
Draw the bubble plot.
Parameters
----------
ax : matplotlib.axes.Axes
labels : list
Labels of the bubbles.
colors : list
Colors of the bubbles.
"""
for i in range(len(self.bubbles)):
circ = plt.Circle(
self.bubbles[i, :2], self.bubbles[i, 2], color=colors[i])
ax.add_patch(circ)
ax.text(*self.bubbles[i, :2], labels[i], color = "w",
horizontalalignment='center', verticalalignment='center')
years = df.year
sites = df.sites
sub_totals = df.sub_total.unique()
y_titles = [1.35,1.2]
fig, axes = plt.subplots(ncols= 2, sharex=True, subplot_kw=dict(aspect="equal"))
x_coord_circles =[0.4,0.5]
for year, y_title, x_coord_circle, sub_total, ax in zip(years, y_titles,x_coord_circles, sub_totals, axes.ravel()):
sites = df[df.year==year]['sites'].values
colors = df[df.year==year]['colors'].values
ax.add_patch(plt.Circle((x_coord_circle, 0.5), 0.6, alpha=0.5, fc= "w",
linewidth=3, ls= "dotted", color="#E8EBEC", transform= ax.transAxes,clip_on=False))
bubble_chart = BubbleChart(area=sites,
bubble_spacing=0.1)
bubble_chart.collapse()
bubble_chart.plot( ax, sites, colors)
ax.set_yticklabels([])
ax.set_xticklabels([])
ax.spines[['left','right','bottom','top']].set_visible(False)
ax.tick_params(length=0)
ax.relim()
ax.autoscale_view()
ax.set_xlabel(sub_total)
ax.set_title(year, y= y_title, weight = "bold")
#add legend
lines = [Line2D([0], [0], color=c, marker='o',linestyle='', markersize=10,) for c in colors]
labels = df.countries.unique().tolist()
plt.legend(lines, labels,
bbox_to_anchor=(-0.2, -0.8), loc="lower center",
ncols = 3,frameon=False, fontsize= 10)
The result:

Reader Interactions