Visualization Techniques for the Comparative Analysis of Weighted Free Trees

A weighted free tree is an undirected connected graph with no cycles whose edges and nodes have weights (positive real numbers). The purpose of our research is to support the comparative analysis of weighted free trees. The fundamental categories of visualization techniques that support comparison are juxtaposition, superposition, and explicit encoding. Juxtaposition is often used for comparison. However, the cognitive load required to grasp a difference is large. Superposition is effective for recognizing a difference, but select information may be difficult to observe. Explicit encoding is an effective technique specialized in a specific task, but representation switching may occur frequently during analysis. Hence, there is the risk of destructing a viewer's mental map, which reduces work efficiency. We divide the working process of analysis into 14 tasks and develop four visualization techniques that can continually perform these tasks. Moreover, we conduct an experiment to investigate whether our proposed techniques are able to perform these tasks. We confirm that these tasks can be performed efficiently by applying our techniques to a case study that compares two trees.