Special issue on diagram aesthetics and layout: Guest editors' introduction

$ Diagrams are an integral part of many visual languages. For diagrams to be an effective and efficient means of communication and visualisation, a layout often has to be produced from data sets that include little or no geometric information. The resulting layout has significant impact on the ability of users to accurately interpret the information contained in the diagrams. Moreover, the choice of which diagram to use for information visualisation can be substantially influenced by aesthetic qualities, such as line styles and colours. This special issue brings together original contributions on both diagram layout and diagram aesthetics into a single collection, to provide a resource for researchers working in this area. This special issue contains four papers, selected from ten papers submitted after an open call. The submitted papers were each reviewed by three anonymous reviewers with the top ranked papers that best fitted the theme of the special issue being accepted. The accepted papers cover topics on graphical cues, graph layout, and the aesthetics of visualisations, alongside an invited survey paper on research into diagram aesthetics and layout. The survey paper, by Helen Purchase, covers 12 years of Diagrams research. Dr Purchase meticulously reviews research presented at the International Conference on the Theory and Application of Diagrams since its inauguration in 2000. This paper demonstrates that, whilst the core topics of interest remain unchanged, there are new and emerging areas in this truly interdisciplinary field. The paper also identifies where disciplines not currently participating in the field might contribute to the diagrams research area. The second paper in this special issue is entitled " Towards a Systematic Understanding of Graphical Cues in Communication through Statistical Graphs " by Cengiz Acartürk. It presents an experimental investigation into the use of graphical cues, using eye tracking techniques. The results reveal that participants in the study are influenced by graphical cues (such as arrows) as well as the type of graph they are viewing. The third paper, entitled " Drawing Layered Graphs with Port Constraints " by Schulze et al., presents a layout mechanism, extending work by Sugiyama et al. by including port constraints. The authors show how their layout algorithm can be used to extend established algorithms by including support for port constraints. They demonstrate that their layout algorithm yields results with few edge crossings and bends compared to competing approaches. The fourth paper is entitled " Preferences for Data …