Hierarchy-based projection of high-dimensional labeled data to reduce visual clutter

- We present an approach to reduce the visual clutter of two-dimensional projections.
- The user can analyze the relationship of clusters on user-defined levels of detail.
- This extended paper adds a magic lens and a user study to evaluate the approach.

Visualizing high-dimensional labeled data on a two-dimensional plane can quickly result in visual clutter and information overload. To address this problem, the data usually needs to be structured, so that only parts of it are displayed at a time. We present a hierarchy-based approach that projects labeled data on different levels of detail on a two-dimensional plane, whilst keeping the user׳s cognitive load between the level changes as low as possible. The approach consists of three steps: First, the data is hierarchically clustered; second, the user can determine levels of detail; third, the levels of detail are visualized one at a time on a two-dimensional plane. Animations make transitions between the levels of detail traceable, while the exploration on each level is supported by several interaction techniques, including halos, a darts view, and a magic lens. We demonstrate the applicability and usefulness of the approach with use cases from the patent domain and a question-and-answer website. In addition, we conducted a qualitative evaluation to assess the usefulness and comprehensibility of our approach.

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