For irregularly measured time-series data, the measurement frequency or interval is as crucial information as measurements are. A well-known time-series visualization such as the line graph is good at showing an overall temporal pattern of change; however, it is not so effective in revealing the measurement frequency/interval while likely giving illusory confidence in values between measurements. In contrast, the bar graph is more effective in showing the frequency/interval, but less effective in showing an overall pattern than the line graph. We integrate the line graph and bar graph in a unified visualization model, called a ripple graph, to take the benefits of both of them with enhanced graphical integrity. Based on the ripple graph, we implemented an interactive time-series data visualization tool, called Stroscope, which facilitates multi-scale visualizations by providing users with a graphical widget to interactively control the integrated visualization model. We evaluated the visualization model (i.e., the ripple graph) through a controlled user study and Stroscope through long-term case studies with neurologists exploring large blood pressure measurement data of stroke patients. Results from our evaluations demonstrate that the ripple graph outperforms existing time-series visualizations, and that Stroscope has the efficacy and potential as an effective visual analysis tool for (irregularly) measured time-series data.

In this paper we present an interactive query interface called "TrapezoidBox" to support spatial proximity queries where users' degree of interest varies depending upon the degree of separation from the point of interest. Spatial proximity queries are commonly built in information seeking tasks especially on online maps. If not impossible, it is hard to formulate spatial proximity queries using existing dynamic query widgets such as range sliders. TrapezoidBox allows users to easily build spatial proximity queries by interactively adjusting a trapezoidal function. Our controlled user study results show that TrapezoidBox has several advantages over a baseline interface with range sliders.