Interactive Similarity Links in Treemap Visualizations

Exploring hierarchical organizations such as software systems is a challenging task. This gets even harder when these are large, deeply nested, and attached by a list of additional attributes of either quantitative, ordinal, or categorical nature. Tree maps have been designed to graphically represent such hierarchical structures in a space-filling way where two attributes for each hierarchy element can be visualized in each tree map box at the same time: by area and by color. Having more than two attributes attached to each hierarchy element can also be visualized by this concept when allowing an analyst to frequently browse the pair wisely represented attributes in the color dimension leaving the box sizes fixed due to mental map preservation. In this paper we enrich standard tree map visualizations by such a browsing feature and additional interaction techniques such as expanding or collapsing them to different levels of hierarchical granularity. To further support the comparison of similar boxes for either one, two, or a list of attributes we add the concept of similarity links whose display thresholds can also interactively be chosen.