A directed graph is said to be a tree if it has a root and there is a unique directed path from the root to every node in the tree. An equivalent characterization of a tree is that the root node has ...

01-27-2015 DESIGN The Medieval Roots Of The Tree Diagram Data viz isn’t just a modern-day craze. Designer Manuel Lima, author of The Book of Trees, discusses the origins of the tree diagram.

Lima includes it in his chapter on figurative tree charts, which are predecessors to more abstract chart techniques derived from tree structures (Sunburst, radial, and Voronoi diagrams).