DATA VISUALIZATION
What to do when pie charts don’t appear to be one of the simplest ways to visualise your information?
Pie charts are probably the most intuitive charts to make use of. They show the distribution of a variable between a number of traits in a compact method. In apply I see many presentation decks from colleagues that use pie charts to show some essential information. Whereas they’re typically related, pie charts are undoubtedly not one of the simplest ways to visualise information for some use instances.
On this article I’ll take the distribution of the world inhabitants by nation for example. In a primary half I need to expose the drawbacks of pie charts and why they don’t seem to be essentially one of the best various when visualizing information. In a second half I’ll current options to show information in a extra related means. This manner you possibly can mirror by yourself use of pie charts and you possibly can select one of the best suited sort of chart on your subsequent information visualization.
The best way to greatest visualize the distribution of the world inhabitants?
That is the core query I’ll attempt to reply graphically all through this text. Let’s think about that I need to current the distribution of the world inhabitants by nation. That is usually a use case the place a substitute for show information — perhaps the primary that may come to my thoughts — is a pie chart.
For example my level I’ll use open information from Our World in Information. You’ll find the supply dataset right here. Primarily based on this information I construct the next pie chart (graph 1). It shows the distribution of the world inhabitants by nation for the 12 months 2021.
Do you discover the earlier graph significant? What does it inform the reader? To be sincere I’d not make certain what conclusions I ought to draw from it. Let me clarify why in 3 questions.
Difficulty #1: It’s onerous to match the scale of an space to a different
In graph 1 you may even see that China has a bigger inhabitants than India however it isn’t apparent, is it? Let’s assume it’s the case. Are you able to inform by how a lot China’s inhabitants is larger than India’s inhabitants?
That is the primary disadvantage of pie charts. Whereas they shortly give insights on orders of magnitude it’s onerous to match two surfaces. It’s notably the case for numerous traits. In our instance the massive variety of international locations makes it virtually inconceivable to match the inhabitants dimension of most international locations.
Difficulty #2: It doesn’t permit to show numerous traits
In graph 1 you see that numerous international locations are displayed within the legend (“223 others”). However may you inform quickly how many individuals do stay in Vatican? And in Benin?
To take action both it’s best to enhance the legend’s dimension quite a bit or zoom into every slice of the pie chart with a mouse-over. As we will inform with this instance pie charts are usually not properly suited to displaying numerous traits.
Difficulty #3: It offers a static overview of a distribution
In graph 1 you possibly can see how the world inhabitants was distributed in 2021. How has it developed over the previous 10 years? To take action you would need to replicate the identical pie chart and adapt the info. In graph 2 I show the world inhabitants in 2011. Are you able to simply inform which nation gained extra inhabitants than one other between 2011 and 2021?
Evaluating two surfaces of pie charts is tough because of the circle form of areas. For the human eye it’s simpler to match two squared surfaces. This is the reason pie charts are usually not the most suitable choice when evaluating two distributions over completely different time frames.
If you end up confronted with the problems talked about above, that is in all probability an indication that pie charts are usually not one of the simplest ways to visualise information on your particular use case. What must you do now? Attempt the next options.
Horizontal bar charts
Horizontal bar charts basically resolve points #1 and #2. As information will not be constrained by the form of a circle, every attribute (in our instance, every nation) may be displayed in a horizontal bar. This permit the reader to simply grasp the scale of a given nation’s inhabitants and to match it to a different nation. If numerous international locations is to show, the variety of horizontal bars will merely be longer — with out impacting the readability of every nation’s information negatively.
That is how the distribution of the world inhabitants in 2021 would appear like in a horizontal bar chart:
Stacked column charts
Stacked column charts slightly resolve points #1 and #3. As additionally they use squared shapes it’s simpler to evaluate surfaces between two international locations or between two time frames. Because the show for a given 12 months is extra compact, such a graph is healthier suited to match the evolution of a distribution over time.
You need to use both the 100% show or the show with absolute values. That is how the distribution of the world inhabitants in 2011 vs. 2021 would appear like in a 100% stacked column chart:
Pie charts are usually not properly suited to all use instances. Their drawbacks could stop finish customers from decoding ends in an actionable means. This is the reason two graphical options assist you to show your information in probably the most acceptable means: horizontal bar charts and stacked column charts.
In the long run what stays fixed is to ask your self why you’re constructing a given chart and what conclusions the tip person could interpret from it. It’s solely when you will have outlined these parts that you could select one of the best type of graph.
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