A partial edge drawing (PED) of a graph is a variation of a node-link diagram. PED draws a link, which is a partial visual representation of an edge, and reduces visual clutter of the node-link diagram. However, more time is required to read a PED to infer undrawn parts. The authors propose a morphing edge drawing (MED), which is a PED that changes with time. In MED, links morph between partial and complete drawings; thus, a reduced load for estimation of undrawn parts in a PED is expected. Herein, a formalization of MED is shown based on a formalization of PED. Then, requirements for the scheduling of morphing are specified. The requirements inhibit morphing from crossing and shorten the overall time for morphing the edges. Moreover, an algorithm for a scheduling method implemented by the authors is illustrated and the effectiveness of PED from a reading time viewpoint is shown through an experimental evaluation.
Partial edge drawing PED is a model for a straight-line drawing of a graph, where edges are subdivided into three parts in order to drop the middle part. Partial Edge Drawing (PED) is a popular graph drawing style aimed at reducing edge crossings and visual clutter. PEDs are straight-line drawings where the central part of each edge is erased, and the length of the two remaining segments are computed so as to preserve useful geometric information. Recent studies on this approach focus on symmetric and δ-homogeneous PEDs (δ-SHPEDs). Given a straight-line drawing, a δ-SHPED of this drawing is immediately defined for a fixed value of δ. In particular, some edge crossings may not be avoidable, although the amount of ink removed from the original drawing might be large (e.g., 50 when δ = 1 4). On the other hand, it is possible to maximize the ink and remove edge crossings by renouncing to homogeneity. We present heuristics to produce symmetric PEDs that are either crossing-free or where crossings forming large angles are allowed. We also describe a user study in which PEDs obtained via our heuristics are compared with the standard model 1 4-SHPED. Our results suggest that the benefit of homogeneity overcomes in terms of readability the benefit of fewer crossings and more ink. Partially drawn links are a possibility to reduce visual clutter in node-link visualizations of relational data caused by link crossings. Although partial links have some benefits concerning task performance, they exhibit issues regarding target node ambiguities. In this paper, we provide the results of a user study that investigates the performance in terms of task accuracy when judging target nodes to which partial links are pointing. We vary the link lengths and link directions as independent variables and measure the task accuracy as dependent variable while the exposure duration for each stimulus is fixed. The major result of our user study is that people tend to make more target node judgment errors with shorter link lengths. Moreover, the direction of the partial links also has an impact on the accuracy. With these results, we are able to choose appropriate parameter settings for graphs drawn with partial links. This can be regarded as a novel graph drawing criterion for improving the readability of graphs represented with partial links.