Authors:
Fabian Beck
1
;
Michael Burch
1
;
Tanja Munz
1
;
Lorenzo Di Silvestro
2
and
Daniel Weiskopf
1
Affiliations:
1
University of Stuttgart, Germany
;
2
Università di Catania, Italy
Keyword(s):
Hierarchy Visualization.
Related
Ontology
Subjects/Areas/Topics:
Computer Vision, Visualization and Computer Graphics
;
General Data Visualization
;
Information and Scientific Visualization
Abstract:
Pythagoras Trees are fractals that can be used to depict binary hierarchies. But this binary encoding is an
obstacle for visualizing hierarchical data such as file systems or phylogenetic trees, which branch into n subhierarchies.
Although any hierarchy can be modeled as a binary one by subsequently dividing n-ary branches
into a sequence of n - 1 binary branches, we follow a different strategy. In our approach extending Pythagoras
Trees to arbitrarily branching trees, we only need a single visual element for an n-ary branch instead of
spreading the binary branches along a strand. Each vertex in the hierarchy is visualized as a rectangle sized
according to a metric. We analyze several visual parameters such as length, width, order, and color of the
nodes against the use of different metrics. The usefulness of our technique is illustrated by two case studies
visualizing directory structures and a large phylogenetic tree. We compare our approach with existing tree
diagrams and discuss
questions of geometry, perception, readability, and aesthetics.
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