  Icicles and sunbursts are two commonly-used visual representations of trees.
While icicle trees can map data values faithfully to rectangles of different
sizes, often some rectangles are too narrow to be noticed easily. When an
icicle tree is transformed into a sunburst tree, the width of each rectangle
becomes the length of an annular sector that is usually longer than the
original width. While sunburst trees alleviate the problem of narrow rectangles
in icicle trees, it no longer maintains the consistency of size encoding. At
different tree depths, nodes of the same data values are displayed in annular
sections of different sizes in a sunburst tree, though they are represented by
rectangles of the same size in an icicle tree. Furthermore, two nodes from
different subtrees could sometimes appear as a single node in both icicle trees
and sunburst trees. In this paper, we propose a new visual representation,
referred to as \emph{radial icicle tree} (RIT), which transforms the
rectangular bounding box of an icicle tree into a circle, circular sector, or
annular sector while introducing gaps between nodes and maintaining area
constancy for nodes of the same size. We applied the new visual design to
several datasets. Both the analytical design process and user-centered
evaluation have confirmed that this new design has improved the design of
icicles and sunburst trees without introducing any relative demerit.

Human-Computer Interaction