This paper presents an analysis of user studies from a review of papers describing new visualisation applications and uses these to highlight various issues related to the evaluation of visualisations. We first consider some of the reasons why the process of evaluating visualisations is so difficult. We then dissect the problem by discussing the importance of recognising the nature of experimental design, datasets and participants as well as the statistical analysis of results. We propose explorative evaluation as a method of discovering new things about visualisation techniques, which may give us a better understanding of the mechanisms of visualisations. Finally we give some practical guidance on how to do evaluation correctly.

A new radial space-filling method for visualizing cluster hierarchies is presented. The method, referred to as a radial clustergram, arranges the clusters into a series of layers, each representing a different level of the tree. It uses adjacency of nodes instead of links to represent parent-child relationships and allocates sufficient screen real estate to each node to allow effective visualization of cluster properties through color-coding. Radial clustergrams combine the most appealing features of other cluster visualization techniques but avoid their pitfalls. Compared to classical dendrograms and hyperbolic trees, they make much more efficient use of space; compared to treemaps, they are more effective in conveying hierarchical structure and displaying properties of nodes higher in the tree. A fisheye lens is used to focus on areas of interest, without losing sight of the global context. The utility of the method is demonstrated using examples from the fields of molecular diversity and conformational analysis.

Inspired by Venn diagram layouts, the Treemap [6] is one of the most prevalent implicit tree visualization techniques. Ever since its publication, it has been modified and extended in many ways. This work presents a way to generate 3-dimensional Treemap visualizations by a 4-step procedure. It can be used for rapid prototyping and comparing different 3D Treemap layout approaches, to devise user studies on 3D Treemap layouts or for educational purposes.

This paper presents an analysis of user studies from a review of papers describing new visualisation applications and uses these to highlight various issues related to the evaluation of visualisations. We first consider some of the reasons why the process of evaluating visualisations is so difficult. We then dissect the problem by discussing the importance of recognising the nature of experimental design, datasets and participants as well as the statistical analysis of results. We propose explorative evaluation as a method of discovering new things about visualisation techniques, which may give us a better understanding of the mechanisms of visualisations. Finally we give some practical guidance on how to do evaluation correctly.

Abstract. The presentation of large hierarchies is still an open research question. Especially, the time-consuming calculation of the visualization and the cluttered display lead to serious usability issues on the viewer side. Existing solutions mainly address appropriate visual representation and usually neglect considering system resources. We propose a holistic approach for the presentation of large hierarchies using treemaps and progressive refinement. The key feature of the approach is the mature use of multiple incremental previews of the data. These previews are well-designed and lead to reduced visual clutter and a causal flow in terms of a tour-through-the-hierarchy. The inherent scalability of the data thereby allows for a reduction in the consumed resources and short response times. These characteristics are substantiated by the results we achieved from a first implementation. Due to its many beneficial properties, we conclude that there is much potential for the use of progressive refinement in visualization. 1