Treemap encodes values as area of nested rectangles for a hierarchy. Ben Shneiderman, University of Maryland, 1991, for disk-space visualization.
In reports, ads and assignments it fits part-to-whole with many leaves and a hierarchy. Skip it when you need precise comparison of similar sizes.
Mistakes
- Failure modes 1 — you need precise comparison of similar sizes
- Failure modes 2 — 3-D pies and perspective bars
- Failure modes 3 — Dual axes that fake a correlation
- Failure modes 4 — Truncated axes that shout a small delta
- Failure modes 5 — Legend only, no direct labels
- Failure modes 6 — Missing source, unit or period
Fixes
- Fixes 1 — Return to part-to-whole with many leaves and a hierarchy.
- Fixes 2 — Flat, one axis, direct labels.
- Fixes 3 — Color-blind-safe palette plus pattern.
- Fixes 4 — Rewrite the title as a claim and add a source line.
Treemap: honour area of nested rectangles for a hierarchy, and switch when you need precise comparison of similar sizes.