Visualization Review: Pie Charts

By July 20, 2017visualization
piefeature

This is the first entry in a series about visualizations. We’ll be going through the most common visualizations out there to gain a better understanding of when and how to use them effectively.

We’ll be starting with the lovely pie chart, which is surprisingly a pretty controversial visualization. Some people love the pie chart and others hate it, but most of the issues arise on how it’s typically used.

When To Use a Pie Chart

Pie charts can be valuable and they look great, when used correctly, but there’s a specific time and place for them (they can be pretty effective for jokes).

The true purpose of a pie chart is to show part to whole comparisons. As in how much of something is made up of specific segment(s). The problem is, this often gets abused and ends up looking like a mess. Exhibit A.

This is completely unusable and the visualization isn’t adding any value. Instead you have to use the labels or tooltips to get any information from the visual and at that point, you may as well be looking at a grid.

Pie charts should be simple and clearly show the part-to-whole comparison that is of interest.

pie

Based on these requirement, your datasets should be small and have at most 6 segments, but even that may be too many.

While there are also different types of pie charts out there, the only ones worth using are the basic and donut variations seen above. Everything else just adds useless bells and whistles that make your visual less effective.

How Not To Use a Pie Chart

Pie charts should be used in a very specific way, but if you’re still not sure how to do that, here’s a simple list of things NOT to do.

1. Don’t make it 3-D

There is no reason to use a 3-D chart. EVER. It adds no value to the visualization and just makes it harder to read. While we’re here, don’t explode the pie chart out either, because it makes it harder to see the part to whole comparison.

2. Don’t use too much data

As mentioned earlier, the fewer segments the better. Pie charts are meant for smaller datasets and simple comparisons.

3. Don’t hide segments

If your pie chart essentially ends up hiding a segment to where it’s not visible, you might want to try a different visualization.

4. Don’t use it for segment to segment comparisons

This is probably the biggest mistake when using a pie chart. It’s almost impossible to compare one segment of a pie chart to another. This is not what they’re for. Focus on the part to whole comparisons or pick something else.

The pie chart is simple and visually appealing, but when it’s misused, it becomes a waste of space. Be aware of how and when you use your pie charts.

Hopefully this was a useful exercise and you have a better understanding of the pie chart. Up next will be the bar chart, so keep a look out.