Information design
Key question
Which representation matches the statement?
Charts reveal patterns that remain hidden in tables. Which visualisation is most suitable depends on what you want to show: a comparison, a trend, a proportion, or a correlation.
Learning objective: You can choose the appropriate chart type for a statement and reduce a visualisation to its core message.
First the statement, then the diagram.
3.1 / From Question to Graphic
Each graphic answers a question.
A visualisation does not begin with the tool, but with the question: What should the viewers understand? From this follows the key message, and from the message follows the chart type.
It is helpful to have a headline that conveys the main finding rather than just the topic: 'Rents rise faster than wages' instead of 'Rents and wages 2015–2025'.
A title is a statement, not a label.
3.2 / Chart types
The message defines the form.
The most common statements and suitable forms:
COMPARISON
Bar
Values of different categories side by side.
DEVELOPMENT
Line
Change over time.
SHARE
Stacked bar
Parts of a whole, or a pie chart if there are few parts.
DISTRIBUTION
Histogram
How values are distributed across a range.
CONTEXT
Scatter plot
Whether two variables are related.
LOCATION
Map
Values by geographic location.
Pie charts are only easy to read with a few slices, as people are worse at comparing angles and areas than lengths.
We compare lengths better than areas.
3.3 / Reduce
Show less, say more.
Edward Tufte coined the term data-ink ratio: the proportion of ink used to actually display data should be as high as possible. Superfluous grid lines, borders, 3D effects, and decorations (chartjunk) are merely a distraction.
Reducing does not mean hiding information. Highlighting through colour or labelling draws the eye to what supports the message.
If it doesn't show anything, it can go.
Exercise
Visualise a statement
Task: Visualise a small dataset, for example your screen time over a week.
STEP 1
Collect the data and formulate a question about it.
STEP 2
Summarise the key message in one sentence.
STEP 3
Select a type using the chart finder and sketch two variants.
STEP 4
Reduce the better variant and give it a descriptive title.
Evaluation: Do others understand your statement without an explanation?