Understanding the limitations of pie charts

Pie charts are a popular and effective way to visually represent data. They are commonly used to show the proportion of different categories in a dataset. However, it is important to understand that pie charts have limitations, and they may not always be the best choice for data visualization. In this article, we will discuss the limitations of pie charts and explore alternative visualization techniques.

Limitation #1: Difficulty in Comparing Multiple Data Points

Pie charts are effective for comparing a single data point to the whole. However, they can be difficult to read when comparing multiple data points. The human brain has a hard time accurately judging the differences in angle sizes, making it challenging to compare the slices of a pie chart. This issue becomes more significant as the number of slices increases.

Let’s consider a dataset with five categories and their respective percentages. We can create a pie chart using matplotlib in Python.

import matplotlib.pyplot as plt

categories = ['Category A', 'Category B', 'Category C', 'Category D', 'Category E']
percentages = [20, 25, 15, 10, 30]

plt.pie(percentages, labels=categories)

Limitation #2: Misrepresentation of Data

Pie charts may misrepresent data if the slices do not accurately reflect the proportions they represent. This issue can occur when there are too many categories, and the slices become too small to distinguish. Additionally, it can be challenging to accurately measure the size of each slice, especially when using a printed or small version of the chart.

Let’s consider a dataset with ten categories and their respective percentages. We can create a pie chart using the same code as before.

Categories = ['Category A', 'Category B', 'Category C', 'Category D', 'Category E', 'Category F', 'Category G', 'Category H', 'Category I', 'Category J']
percentages = [5, 5, 5, 5, 5, 5, 5, 5, 5, 50]

plt.pie(percentages, labels=categories)

Limitation #3: Difficulty in Showing Changes Over Time

Pie charts are not well suited to display changes over time. It can be challenging to compare pie charts from different time periods, and it can be difficult to see changes in the proportion of categories from one period to another.

Let’s consider a dataset with three time periods and their respective category percentages. We can create a stacked bar chart using matplotlib in Python to better visualize changes over time.

import numpy as np

time_periods = ['Period 1', 'Period 2', 'Period 3']
categories = ['Category A', 'Category B', 'Category C']
percentages = np.array([[20, 25, 15], [30, 20, 10], [10, 15, 30]])

fig, ax = plt.subplots()
ax.bar(time_periods, percentages[:, 0], label=categories[0])
ax.bar(time_periods, percentages[:, 1], bottom=percentages[:, 0], label=categories[1])
ax.bar(time_periods, percentages[:, 2], bottom=np.sum(percentages[:, :2], axis=1), label=categories[2])

Pie charts are an effective way to visualize data, but they have limitations, especially when dealing with multiple data points, small slices, and changes over time. It is essential to consider the dataset’s characteristics and purpose before choosing a data visualization technique. In some cases, alternative visualization techniques, such as stacked bar charts or treemaps, may be more effective in displaying data accurately and meaningfully

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