Pick the chart by the question, not by what looks interesting. Find your question in the first column.
The chooser
| Your question | Use | Notes |
|---|---|---|
| How do categories compare? | Bar chart (horizontal if labels are long) | Sort by value unless the categories have a natural order. Start the axis at zero. |
| How does something change over time? | Line chart | Time runs left to right. Use a few lines at most. |
| How did a single value change between two points? | Slope chart or a simple pair of bars | Shows direction and size without clutter. |
| How are values spread? | Histogram or box plot | A histogram shows the shape; a box plot compares several groups. |
| How are two numbers related? | Scatter plot | Add a trend line only if the relationship is the point. |
| What is the share of a whole? | Stacked bar, or a pie for two to four parts | Parts must add up to something that makes sense as a whole. |
| What are the exact values? | Table | When people need to look up numbers, a table beats any chart. |
| How does a total break down step by step? | Waterfall chart | Good for revenue bridges and budget changes. |
| Where is something happening? | Map | Use only when location is the point. A bar chart by region is often clearer. |
| How does one measure compare across many items at once? | Heat map | Colour shows size; add values if precision matters. |
Common mistakes
- A pie with many slices. People cannot compare angles well. Use a sorted bar chart.
- A truncated bar axis. Bars encode value by length, so cutting the axis exaggerates differences.
- Too many lines. More than four or five lines becomes spaghetti. Highlight one and grey out the rest.
- Dual axes. Two scales on one chart let you make any two lines appear to move together.
- Colour that means nothing. Use colour to carry a meaning, such as highlighting the one category you are talking about.
- 3D. It distorts the sizes it is trying to show.
Before you publish
- State the point of the chart in its title, in a sentence ("Support tickets fell 20% after the update").
- Label the axes with units and the time range.
- Remove everything that is not needed: gridlines, borders, legends that repeat the labels.
- Ask someone who has not seen it what it says. If their answer is not yours, change the chart.
From Grokem: https://www.grokem.com/data/visualisation/charts-and-graphs/chart-chooser-reference
