12. What Charts Not to Use

 
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Overview

PowerPoint provides a number of charts which are not easy for an audience to grasp. Here I outline which charts I tend to avoid and suggest some better alternatives.

Lesson Notes

A list of what charts not to use

1 Pie charts: Our eyes cannot measure angles as well as distances
2 Donut charts: Our eyes cannot measure angles as well as distances
3 Radar charts: 5 different axes are different to read along with overlapping data
4 3-d surface chart: Extremely difficult to read even for small datasets

Transcript

While it’s important to know how to use the various chart types in PowerPoint, it’s just as important to know what charts not to use.

In this lesson, I’ll go over some charts which I think are very difficult for an audience to intuitively grasp, and therefore should be avoided.

I’m going to start with a common chart type, the Pie chart.

Unfortunately, our eyes are not as good at measuring angles as we are at measuring length or distance.

Let’s take this example of two Pie charts.

In each chart, can you tell which segment is the largest of the five? Quite difficult, isn’t it? Now let’s try it when the information is represented on a Bar chart.

On the left we can see that the red segment is the biggest, and on the right, the green segment. So if you can help it, always avoid using the Pie charts if possible.

Needless to say, this insight also applies to the Donut chart.

The next chart to avoid is the Radar chart or Spider chart.

This is often used when comparing different characteristics for a set of products.

In this case, a car.

Radar charts are notoriously difficult to read and should be avoided if at all possible.

The first problem with the Radar chart is occlusion, which means part of the visualization obscures another part.

For Radar charts this is inevitable when multiple series are plotted.

The next issue for the Radar chart are the angles of the axes, which are all different from each other, which makes the Radar chart much harder to read than a Line chart, which will have parallel axes.

As an alternative to the Radar chart, why not just use a simple Line chart with each type of car in this case, getting a separate line colour.

For me this is a much easier chart to read.

The last chart I’d encourage you to avoid is the 3-d surface chart.

As you can see from this example, it’s very difficult to make any sense from this chart, and it will be sure to confuse your audience, even if they are impressed by the 3-d visualization.

Although they may seem boring and pedestrian, two dimensional Bar charts and Line charts can serve almost all of your charting needs.

Sometimes they’re made to be stacked or grouped, but audiences find them intuitively easy to read, and as a result, should be your first port of call when creating charts.