Chord and Sankey diagrams are two common techniques for visualizing flows. Chord diagrams use a radial layout with a single circular axis, and Sankey diagrams use a left-to-right layout with two vertical axes. Previous work suggests both strengths and weaknesses of the radial approach, but little is known about the usability and interpretability of these two layout styles for showing flow. We carried out a study where participants answered questions using equivalent Chord and Sankey diagrams. We measured completion time, errors, perceived effort, and preference. Our results show that participants took substantially longer to answer questions with Chord diagrams and made more errors; participants also rated Chord as requiring more effort, and strongly preferred Sankey diagrams. Our study identifies and explains limitations of the popular Chord layout, provides new understanding about radial vs. linear layouts that can help guide visualization designers, and identifies possible design improvements for both visualization types.

Comparative analysis in genomics involves comparing two or more genomes to identify conserved genetic information. These duplicated regions can indicate shared ancestry and can shed light on an organism's internal functions and evolutionary history. Due to rapid advances in sequencing technology, high-resolution genome data is now available for a wide range of species, and comparative analysis of this data can provide insights that can be applied in medicine, plant breeding, and many other areas. Comparative genomics is a strongly interactive task, and visualizing the location, size, and orientation of conserved regions can assist researchers by supporting critical activities of interpretation and judgment. However, visualization tools for the analysis of conserved regions have not kept pace with the increasing availability of genomic information and the new ways in which this data is being used by biological researchers. To address this gap, we gathered requirements for interactive exploration from three groups of expert genomic scientists, and developed a web-based tool called SynVisio with novel interaction techniques and visual representations to meet those needs. Our tool supports multi-resolution analysis, provides interactive filtering as researchers move deeper into the genome, supports revisitation to specific interface configurations, and enables loosely-coupled collaboration over the genomic data. An evaluation of the system with five researchers from three expert groups provides evidence about the success of our system's novel techniques for supporting interactive exploration of genomic conservation.

Professional training often requires need-based scheduling and observation-based assessment. In this paper, we present a visualization platform for managing such training data in a medical education domain, where the learners are resident physicians and the educators are certified doctors. The system was developed through four focus groups with the residents and their educators over six major development iterations. We present how the professionals involved, nature of training, choice of the display devices, and the overall assessment process influenced the design of the visualizations. The final system was deployed as a web tool for the department of emergency medicine, and evaluated by both the residents and their educators in an uncontrolled longitudinal study. Our analysis of four months of user logs revealed interesting usage patterns consistent with real-life training events and showed an improvement in several key learning metrics when compared to historical values during the same study period. The users' feedback showed that both educators and residents found our system to be helpful in real-life decision making.