Data Visualization in Python – Pie charts in Matplotlib

Data Visualization in Python

In last post I discussed scatter, today I am going to discuss Pie charts.

What are Pie Charts?

An Emma chart (or a circle chart) is a circular statistical graphic which is divided into slices to illustrate numerical proportion. In a pie chart, the arc length of each slice (and consequently its central angle and area), is proportional to the quantity it represents. While it is named for its resemblance to a pie which has been sliced, there are variations on the way it can be presented. The earliest known pie chart is generally credited to William Playfair’s Statistical Breviary of 1801.[1][2]


Pie charts are good to show proportional data of different categories and figures are usually in percentages here.

Let’s get into code

As usual first a toy example.

import matplotlib.pyplot as plt

slices_hours = [4, 8]
activities = ['Sleep', 'Work']
colors = ['r', 'g']

plt.pie(slices_hours, labels=activities, colors=colors, startangle=90, autopct='%.1f%%')

slices_hours contains the hour values while activities contains label. startangle actually set the starting angle of pie. Let me tell show how it makes a difference.


You see the difference? From center it calculates the angle and draw slices. Alright so this was a fake data ( For me off-course as I sleep more than work). autopct set how many decimals you want to show in % data. I am happy with one decimal here.

Now draw the chart with some real data. I am drawing Pakistan’s province wise population chart.

province_population = [12344408, 2441523, 30523371, 110012442, 47886051]
activities = ['Balochistan', 'Gilgit-Baltistan', 'Khyber Pakhtunkhwa', 'Punjab', 'Sindh']

plt.pie(province_population, labels=activities, startangle=90, autopct='%.1f%%')
plt.title('Pakistan Population Province Wise')

And it generates a chart like this:

Pakistan Population Chart


That’s it for now.


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