The worst diagram in the world is
And here we are launching the next course stream. "The jаvascript Developer" and, on the recommendation of teachers , prepare interesting materials for reading. Today, let's look at one interesting note about visualizing the output of data.
A pie chart is the most terrible way of transmitting information ever invented in the history of data visualization.
Of course, there are more inconvenient methods. But none of them has the popularity and confidence to the same extent as the pie chart.
Come on, I'll explain what's wrong with her, and why you need to stop using it as soon as possible.
First, let's talk about why we generally use diagrams:
Diagrams are a way to take some information and make it more understandable.
In general, the task of diagrams is to simplify the comparison of different sets of data.
The more information the diagram is able to convey without increasing complexity, the better.
I will show how a pie chart fails on all these criteria. The "task" of the pie chart is to show the relationship between the parts and the whole.
Let's see how badly she copes with the only task for which she was allegedly created. Look at these three pie charts. Suppose they reflect the distribution of votes in local elections between five candidates in three different observation intervals A, B and C:
Open source /Wikipedia
So, what can we learn from this information? Since these proportions of votes that each candidate received, the reader should easily understand what is happening in the race. But this is not so. Does candidate 5 have better results than candidate 3? Who showed the best result in time A and B - Candidate 2 or Candidate 4? Who has the greatest momentum in the race?
So if the task is to make the information easier to understand, how much have these diagrams helped you? Really, if I just gave you a table with the voices values, would not it be easier to perceive the information?
But for now look at the same information presented in the form of a histogram:
Now it is much clearer. At first glance, we can understand what exactly happens to each of the candidates in each period of time of the race. This histogram distinguishes much more clearly the parts of the whole than the pie chart, despite the fact that this is its main task.
Let us now look at another drawback of the pie chart, which is connected with the fact that people do not really understand the circles.
Below is a pie chart showing the distribution of parties of the European Parliament:
The main question is - can we compare the shares to reveal the differences in the sizes of all parts of the diagram? If the only thing we're trying to find out is that EPP is bigger than S & D, then what's the point in the diagram? I could understand this by simply looking at the two numbers. No, the diagram is useful only if we can compare all its elements with each other.
Below are the individual shares, for comparison, taken out of context. Look at them, and think, can you arrange them in order from the largest to the smallest.
People generally do not know how to compare the proportions of a circle when it comes to size.
That's why you could consider trigonometry and radians much more complicated than the usual geometry of rectangles.
It's not bad, but it's worth keeping in mind when trying to formulate information in the most exhaustive and accessible way. Here are the same data, but in the form of a bar chart:
Note that you can compare each lot with any other batch.
Simply compare the lengths of the rectangles to understand what is happening.
With a strong desire, you could replace the left axis with interest to know the distribution within the parliament. Now you can see how many seats are assigned to each of the parties - this information was not originally presented on the pie chart.
And now, let's see how easy it is to manipulate pie charts.
Here are the same data as above, but now in the form of a 3D Circular Diagram:
People always use this, because a three-dimensional pie chart, at an angle, is a great way to deceive you. Look at the diagram, S & D - the red party - looks roughly equal to the EPP blue-green batch. But this impression is created only because I distorted the perspective, creating the impression that the red is big.
It's so simple that it's even a little embarrassing that Excel allows you to do this.
Below is another example of the lack of a pie chart. In fact, 10% of the men reading this article will not even understand what is being said.
Red-green color blindness in men
The most elegant diagrams do not require labeling of data. To convey a thought, extraneous numbers are not required. And if required, you use the wrong diagram.
So, let's draw conclusions:
If in the information provided there are shares of similar sizes, a pie chart is an unsuitable choice.
If the results of observations are several (3 or more), the pie chart is an unsuitable choice.
A pie chart can easily be abused.
A pie chart is an unsuitable choice, if you need to label each percentage.
Before moving on to the final criticism of the pie charts, let's see what they are all the same good. The only situation in which pie charts are good is the comparison of 2-3 observation results with a very different amount of information.
Business Insider, data from Detroit
Paid and unpaid real estate taxes in Detroit, 2011
And that's all.
That is, if you think, the only thing they are good at, the only way to use them is to show people how they look. The only problem of the diagram above is to show how 32 of 100 looks like.
Last week I commented on , that the pie chart is Nickelback from the world of data visualization. This attack spread widely. But I came to the conclusion that there is even a more suitable metaphor. Pie charts - Aquaman from the world of data visualization.
Aquamen is good only in one. Even so, other DC superheroes can often perform Aquaman's work better than himself. Superman will hold his breath under the water, Batman simply has a submarine. If an oil tanker drowns, who will you call? Aquamena? Or Superman? You start to wonder why Akvamena was invited at all.
And when there is a real chance for Aquaman or a pie chart to be useful - maybe you need to talk to the fish or explain what the 32% looks like in the circle - there is a doubt as to whether it is necessary at all. Just stop using pie charts. They are useless, they can easily be fucked up, and they do not cope with the only task of the diagrams - to make information visually vivid. Pie charts are Aquaman.
So what to use?
As tweeted Edward Tufte, a date-scientist who wrote in detail about the failure of the pie chart:
Users of pie charts deserve the same suspicion + skepticism that people who are confused can not. For comparison, use small tables, sentences, but not pie charts. Edward Tufte (@EdwardTufte)
As always, we are waiting for questions and comments here or you can go to open house day to Alexander .
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