The TreeMap is a constant area visualisation invented by Ben Shneiderman for hierarchical data with some form of numerical attribute, for example the sizes of files and folders on a computer disk. The most basic form starts with a rectangular area and then recursively divides the area alternatively horizontally using the total values for each level.

Used on page 135

### Links:

- cs.umd.edu: Treemaps for space-constrained visualization of hierarchies
- Wikipedia: Treemapping
- upload.wikimedia.org: Treemap of Singapore Exports in 2012 organised by product type. Gordon.silvermanaz, CC BY-SA 4.0, via Wikimedia Commons