Avoid 3D charts
Experts agree that 3D effects should be used only if absolutely necessary. In most instances, they only offer aesthetic appeal and do not add anything to the interpretation of the data. The perspective can distort the data in a sense that what is displayed “in front” is perceived as more important than what is shown in the background.
Use pie charts with care
You should try to minimise the use of pie charts as they can be difficult to understand because our visual perception is not designed to accurately assign quantitative values to two dimensional areas.
More information on this topic can be found in the type of charts section.
Include zero on the axis
This rule is especially important when using bar charts. Because we judge the values in a bar chart by the lengths of the bars, not by the positions of the ends of the bars, the axis scale must include zero. By chopping off the bottoms of the bars, we increase the resolution of the chart, but we distort the apparent values encoded by the bars.
Other types of chart can also distort the relative values if the zero is not included on the axis scale because they are likely to exaggerate differences between values.
If your data set consist of only high numbers and could be better presented without starting your values at a zero, a dot plot could be an answer to your problem. More information about dot plot can be found in the type of charts section.
Order the numbers
When displaying data in pie or bar charts, it helps when the chart’s elements are ordered by their value. In this way, it will take less effort to discover the ranking order.
Use colour sparingly
The use of colours in analytics, should add meaning and extra context to the visualisation. It should not be used merely to make the charts look pretty.
More information on this topic can be found in the Use of colour section.
It can help your audience to draw their attention to exceptional categories in your charts. For example highlight the biggest or the smallest values in a different colour.
If your chart is showing a couple of outliers and you know the reason, you could add annotations to these specific data points.
Test your own knowledge
We have found this online test designed by Stephen Few, a great way of checking your own understanding of the principles of good design. It’s a fun way of learning and consolidating your knowledge. The Graph Design IQ Test is a simple Flash application that contrasts bad practices that are common with effective practices in a way that is entertaining and educational.
Don’t confuse data visualisation with data art
There are two distinctive approaches to presenting data in a graphical form: data visualisation and data art. According to Few (2012), these two concepts have a different purpose and design and should not be confused. The main job of the data visualisation is to inform and help the understanding. The primary purpose of the data art is to deliver an aesthetically pleasing experience and to entertain.
The purpose of visualisation is insight, not pictures.