In my previous post on Data Visualisation, I highlighted the four key principles for good visualisation:
- Design for your audience: Think about how to emphasise the key point(s) that you are trying to convey to this audience with this particular visualisation
- Accurately represent the data: The visualisation should show the underlying data without distortion, and avoid common pitfalls that obscure the real information.
- Organise the information: The visualisation should have a clear purpose - communication, exploration, tabulation or decoration.
- Keep it clear: The visualisation should focus on the message(s) for the audience, and all visual clutter kept to a minimum (except where useful to highlight key points).
Design for your audience
- Test your visualisation with your key audience
- Know when to use dynamic tools, when to use charts, and when to use tables
- Limit the number of categories shown in a visualisation - be selective in what you present in order to emphasise the key message(s)
- Don’t distort the scale to give undue weight to statistically insignificant data
- Keep the zero on the axis scale
- For bar-charts, set the base of the bars to zero (not the lowest value)
- Avoid varying the size/area of objects in graphs, except to convey difference in values
- Avoid using line charts where data is only available for a small number of data points
- Bar graphs are good for showing how data changes over time.
- Pie charts are visually simple and easily understood, but can be manipulated to give a false impression.
- Scatter graphs or line graphs are used to investigate the relationship between two variables, providing sufficient data points are available.
- Bubble charts or triangular graphs can be used to show how the relative dominance of one or more factors combined can influence direction of travel.
- Radar or kite charts are good for comparing multiple factors for different options.
- Choropleth/Isopleth maps show areas shaded according to a prearranged key.
- Treemaps display hierarchical (tree-structured) data as a set of nested rectangles.
- Sound and motion can be used to show changes over time, or changes based on dynamic variables.
- Avoid using purely decorative effects such as 3D that can hide the data
- When choosing a colour palette, limit the number of colours used and ensure that different colours can be distinguished from each other
- Where colour is needed, use solid blocks of colour and avoid complex fill patterns
- Avoid using strong or bold colours for the background in a visualisation
