The charts are there to help us to understand more about the data. But it’s so easy to design a bad visualization. In general, the point of charts is to make it easier to compare different sets of data. The more information a chart is able to convey without increasing complexity, the better.
The primary strength of a pie chart is the part-to-whole relationship, however, pie charts only make it easy to judge the magnitude of a slice when it is close to 0%, 25%, 50%, 75%, or 100%. Pie charts visual attributes is hard to compare.
Here’s a pie chart of the party breakdown of the European parliament:
Can we really compare the slices to figure out the distinctions in size between each and every pie slice? The only thing that is obvious to us is that the EPP and S&D are bigger than any other pieces. And the color of each individual slices are very similar, make it very hard for users to match the label to each slice.
Moreover, people love dressing up their pie charts today. Adding a third dimension of depth to the picture, throwing in some lighting effects and contoured edges. It’s pretty and eye-catching, but is it more meaningful or easier to interpret? Actually, by adding depth to the pie and changing its angle, we’ve made it more difficult to interpret. People do this all the time, and that’s because an angled 3D pie chart is an excellent way to lie to you.
Looking at this chart, S&D — the red party — appears to be roughly even with EPP, the teal party. It looks greater than it actually is, because of the depth that’s been added. The slices are now more difficult to compare, because the angle skews their appearance.
If we take out each individual slices, will that make it easier to compare each individual slice and figure out an ordering from largest to smallest? The reality is, humans aren’t very good at comparing slices of a circle when it comes to size.
Dashboard is to present information in a way that can be quickly read and easily understood. Bar charts makes it better to compare the magnitudes of each part.
Here is a bar charts of the same date. You can compare each and every party to each and every other party. You’re just comparing the length of rectangles in order to understand what’s going on.
If a bar chart is doing its job, you shouldn’t have to struggle. Just save the pies for desserts.
Reference:
http://www.businessinsider.com/pie-charts-are-the-worst-2013-6
The Worst Chart In The World
https://www.perceptualedge.com/articles/visual…/save_the_pies_for_dessert.pdf
Save the Pies for Dessert