Follow these steps to improve your chart design 

misleading

Design that misleads the reader, should be avoided always

confusing

Chart design that might confuse the reader

color

Make your chart pleasing to look at with intentful use of colour

storytelling

Design that improves the chart and helps you tell a visual data story.

Some design in charts will mislead people. Whether the design is used with intend or not. These design choices should be avoided at all times. 

True scaling, bar or column chart, start at zero

When the Y axis at a barchart of a column chart does not start at zero, people will intuitively start comparing the length of the bars. Because bars are only shown partially, the are mislead in their interpretation. 

If you are lucky, they will look further and find out that their first conclusion was not correct. If not, you have given them false information. 

True scaling, only use one y-axis

When the Y axis at a barchart of a column chart does not start at zero, people will intuitively start comparing the length of the bars. 

If you are lucky, they will look further and find out that their first conclusion was not correct. If not, you have given them false information. 

Change confusing design

Chart design that is not neccessary wrong, but is confusing for the reader te interpret. Therefore it should not be used.

Use four series maximum

The working memory of a human brain can only process 4 elements at the same time. So do not use more than four series in your chart. If you have more series, solutions can be:

– split you chart into a small multiple construction with each a single serie
– aggregating smaller series into a bigger “other” serie. 

Make straight corners

Fluid lines look beautifull, but creates distortion to the data values.

In the example on the left, data is never negative, but when the lines are made fluid, the line crosses the x-axis. 

Do not use 3D

If 3D is used in a visualisation, is becomes harder to read the values of a chart. 

Use your colors with intent

Color is one of the most powerfull visual elements, so you must use it with intent

It is about the data, not the axis

“Above all else show the data” is a famous quote of Edward Tufte. 

If a chart has black axis, it will draw the attention away from the data, therefore you should make you axis grey. 

Use colors sparingly

If your series are of the same measure and you do not need color to separate them visually, you should stick to just one color. 

Tell your story

Once you cleaned up you chart, time has come to add design so your chart tells a story to your audience. 

Use relevant ranking

When you rank your data, it will be simpler to process for the human brain. Outliers or strange things will appear more clearly.

Ranking must be relevant. If you make one chart that shows the scores of 50 students, who need to find their own name in the visual, alphabet might be a better choice than ranking by size. 

Highlight what is important

Once all series have the same color, you can add color to the one series that you want to emphasize.