How to create better charts? Search the web and you’ll find many specific advices, not always backed up by scientific evidence (can there be any?). Tufte’s advices are great for us, rational, positivist members of the human race, but what about those emotional poor fellows for whom a minimalistic chart is just a boring chart?

Can we remove personal aesthetics from the equation? Probably not, but we can minimize it. And if you have a set of basic principles that acts as a framework and guides you through the selection and design of charts you’ll end up getting a more efficient display than just relying on your preferences of the moment.

This six-part series focus on the generic design principles of simplicity, consistency, compatibility, congruence, relevance and conventionality (there will be a separate post for each one). These principles are defined by Michael Schiff in his master’s thesis, “Designing Graphic Presentations from First Principles” (you can get the PDF file here).

Let’s start with simplicity

The simplicity principle

The simplicity principle states that a “simpler” chart will be easier to understand. By “simpler” it means fewer types of objects and properties used to encode information. This can be linked to Tufte’s minimalistic approach (the data/ink ratio, maximization of data density, no “chart junk”…) but extends beyond that, while having a more abstract nature.

What happens when you apply this principle to the well known Excel chart defaults? You can see it on the left: after an extreme makeover you can really see the data on the second chart. There is a quote by Michelangelo that expresses quite well what happened: “I saw the angel in the marble and carved until I set him free.

Note that each of the formatting options has a different nature:

  • The gray background is pure chart junk and must be removed;
  • The decimal place on the Y-axis gives us an irrelevant illusion of precision that doesn’t make sense; you can also remove the percent sign;
  • The gridlines are supporting actors that you can leave muted in the background;
  • Removing the legend and replacing it with direct labeling of each series has a deep impact on the user experience: there is no need for the movement of the eyes between the data and the legend and you can free up your working memory;

As you can see, the simplicity principle alone can improve dramatically your chart message. Please remember: a chart is not a product, a chart is a delivery boy.