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Baking another Pie(chart)?? Pause and Read ahead!

As a data enthusiast, I love finding ways to present data clearly and help people make better decisions. Visualization techniques using charts and graphs should make data easier to understand and analyze without increasing the complexity of what’s being presented. This article will look into the pie chart, a widely used chart type in data visualization, and explore its alternatives.


Table of Contents:

1. Introduction

2. What Is A Pie Chart?

3. Limitations Of A Pie Chart

4. Alternatives To Pie Charts

5. Conclusion


1. Introduction


One of the most overused charts in Tableau and data visualization, in general, is the pie chart. It is a popular choice to represent a part-to-whole relationship, but their effectiveness in describing and interpreting data is still debatable. It is essential to be aware of the limitations of a pie chart and consider alternative chart types that may be more suitable to present the data accurately.


Let's dive deep …


2. What Is A Pie Chart?


A Pie chart is a circular chart with slices or sectors to display data as a percentage of a whole. As the name suggests, it resembles a pie, where the circle represents the whole (100%). Each slice represents a category or value that compasses the total and how much of a whole an individual part takes up. They are simple and easy to construct, making them accessible to various audiences. This chart helps the user to compare the relationship between different dimensions (Eg. categories, products, countries, etc.) within a specific context.


3. Limitations Of A Pie Chart

  • Clear labeling is required to communicate effectively- taking up too much space to convey very little information.

  • At most, five categories can be represented - the more slices, the more clutter.

  • Hard for humans to estimate quantity from an angle and compare different sections of a pie chart.

  • Challenging to use it for illustrating changes over time- comparing similar slices from different pie charts can take much work to interpret.

  • Cannot be used when the percentages don’t measure to 100 percent.

  • Negative values or complex fractions cannot be represented.

Try it for yourself :


I have used the Sample Superstore data set to create a pie chart to show the sales percentage for the

"SubCategory."





​Please observe how difficult it is to interpret data without proper labeling. Also, the smaller portions of the pie cannot be distinguished clearly.

​The data is sorted and labeled. The highlighted section clearly shows a crowded chart, making reading and interpreting data difficult.

It is best advised to use a pie chart if you have 2 - 5 categories, ideally 2 - 3. So let’s keep it simple and try to analyze the sales percentage of the " Category " instead of "Subcategory".


Even though we have only three categories, it is challenging to compare the slices with similar proportions and draw conclusions from them.

4. Alternatives To Pie Charts


Decisions based on visual impact rather than data analysis can lead to inaccurate conclusions. Our brain is better suited to compare angles and slices, but we can quite easily compare differences in rectangular shapes. Keeping in mind the shortcomings of pie charts, let's consider the alternatives for it. Let’s start with Bar Chart and its variations.


Bar Chart

While not the most flashy among the charts, they are easy to understand and straightforward to interpret - Simple yet effective. A bar chart represents data using rectangular bars, either horizontal or vertical. The height or length of each bar is proportional to the value or frequency it represents. To further enhance the clarity, horizontal bar charts can be used to make it easier to distinguish between values.






Pie Chart to Horizontal Bar


A glance is enough to tell the difference between each category, not just the largest. The similar-looked slices in the pie chart have much more apparent proportions in the horizontal bar chart.



Even though an effective chart, some of you think of it as a boring chart… right?

Edward Tufte warns in his book Envisioning information: "Cosmetic decoration, which frequently distorts the data, will never salvage an underlying lack of content."

Let’s ignore his warning for a bit and discuss our next alternative.

All who are kids at heart, this way, please …. Lollipop Chart it is!


Lollipop Chart

These are bar charts with skinny bars and bubble markers on top. This chart is a variation of the traditional bar chart where the bubble or circle represents the data point, and a line is drawn from the point to the horizontal axis.







Pie Chart to Lollipop Chart


Like the bar chart, it is easier to read and compare values between different data points but an alternative to it, as it reduces clutter and highlights top values.



Wait a min…..Is anyone here wondering whether we comprised the “part-of-the-whole” concept pie charts are still best known for? Hmmm…We can, however, still show it by labeling the bars with percentages. But for those who do not want to settle for the workaround and go with what it was initially meant for, let’s go with the stacked bar chart.


Stacked Bar chart

This is a type of bar chart where a bar is divided into segments, each representing a different category or value. The segments are stacked on top of each other, so each bar's width or height (depending on its orientation) represents the total value for that category or group. These are the closest linear equivalent to pie charts.







Pie Chart to Stacked Bar Chart


No potentially misleading angles to comprehend. The overall distribution of values and the contribution of each category to the total value is represented. It provides a cleaner visual as the labels can sit inside the chart itself and, depending on the data, often do not require a legend.



The next one is great at picking vast amounts of data and then depicting it in a compact, visually appealing, and easy-to-read manner.


Tree Map

Primarily meant for displaying the hierarchical breakdown of data, tree maps have come more recently into favor as a pie chart alternative. This data visualization strategy uses rectangles of varying sizes inside a single rectangle. Combined, the rectangles represent 100%, with each section accounting for a proportion of the total.





Pie Chart to TreeMap


Instead of staring at those tiny little slices in a pie chart, we can easily read the tree chart and make comparisons quickly. Each pie slice has an equivalent tree rectangle in this regard. By default, each category will be ordered from highest to lowest, with the most significant proportion in the top left and the smallest in the bottom right. It is particularly used when a large amount of hierarchical data needs to be visualized in a smaller space.


Anyone up for square pies?? Yes, let's explore the waffle chart.


Waffle Chart (Detailed Explanation here)

As the name implies, a waffle chart has a similar appearance to a waffle. Unlike tree maps that use rectangles of different sizes, waffle charts use evenly-sized segments. Typically, they are composed of a 10x10 grid of squares, with each square representing 1%. In total, the grid has 100 squares representing 100%. The colored squares in the chart indicate the percentage of a given value. Overall, waffle charts are easy to interpret.





Pie Chart to Waffle Chart


At a glance, the waffle chart offers the same information as a pie chart but, at the same time, permits a deeper analysis of how the data compare. Instead of relying on angles to read the data in the pie chart, here we estimate the approximate proportions (even without labels) by counting the cells where each represents 1%. Hence making it easier to interpret the data. It is more visually appealing, too, particularly when we become tired of seeing pie charts in visualizations.


Conclusion

Pie charts are not recommended for comparing data and should only be used sparingly. If you use pie charts, it's essential to display percentages and arrange the slices by size while keeping the number of slices to a minimum to make them more readable. Overusing pie charts can indicate a need for more consideration for effective data presentation. The article recommends using alternative charts instead of pie charts to improve visualizations, but choosing the appropriate one for the intended purpose is crucial.


Thank you for reading!


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