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.
Rules
- Rules 1 — Use area of nested rectangles for a hierarchy as one channel, not two.
- Rules 2 — Direct labels beat a distant legend.
- Rules 3 — Do not hide zero. If you break the axis, say so.
- Rules 4 — Colour encodes category or magnitude, not both.
- Rules 5 — Put the claim in the title, not just “Treemap”.
- Rules 6 — Source and period, even in small type.
Palette
- Palette 1 — Categories: distinct hues. Sequences: one hue, changing value.
- Palette 2 — Diverging: a neutral centre, emphasis at both ends.
- Palette 3 — One brand colour plus greys beats a rainbow.
- Palette 4 — Check contrast on a projector and in greyscale print.
Type
- Type 1 — Tabular figures for numbers. Do not pour body copy into the chart.
- Type 2 — Titles as sentences; axes as short nouns.
- Type 3 — For CJK, drop weight one step and leave tracking.
Treemap: honour area of nested rectangles for a hierarchy, and switch when you need precise comparison of similar sizes.