Margit Pohl

Solving Problems with Visual Analytics

Visual analytics is an emerging research discipline aiming at making the best possible use of huge information loads in a wide variety of applications by appropriately combining the strengths of intelligent automatic data analysis with the visual perception and analysis capabilities of the human user. The major goal of visual analytics is the integration of these disciplines into visual analytics to acquire well-established and agreed upon concepts and theories, combining scientific breakthroughs in a single discipline to have a potential impact on visual analytics and vice versa. In a session at FET’11, the leaders of the thematic working groups of the recently finalised FET Open coordination action VisMaster CA presented the scientific challenges that were identified in the visual analytics research roadmap, and the connection between the various disciplines and the broader vision of visual analytics. This article contains excerpts from this research roadmap to motivate further research in this direction within FET.

Visually exploring multivariate trends in patient cohorts using animated scatter plots

The effectiveness of animation in visualization is an interesting research topic that led to contradicting results in the past. On top of that, we are facing three additional challenges when exploring patient cohorts: irregular sampling, data wear, and data sets covering different portions of time. We present TimeRider, an improved animated scatter plot for cohorts of diabetes patients that tackles these challenges along with its evaluation with physicians. Results show that animation does support physicians in their work and provide further domain-specific evidence in the discussion on the effectiveness of animation.

The User Puzzle—Explaining the Interaction with Visual Analytics Systems

Visual analytics emphasizes the interplay between visualization, analytical procedures performed by computers and human perceptual and cognitive activities. Human reasoning is an important element in this context. There are several theories in psychology and HCI explaining open-ended and exploratory reasoning. Five of these theories (sensemaking theories, gestalt theories, distributed cognition, graph comprehension theories and skill-rule-knowledge models) are described in this paper. We discuss their relevance for visual analytics. In order to do this more systematically, we developed a schema of categories relevant for visual analytics research and evaluation. All these theories have strengths but also weaknesses in explaining interaction with visual analytics systems. A possibility to overcome the weaknesses would be to combine two or more of these theories.

TimeCleanser: a visual analytics approach for data cleansing of time-oriented data

Poor data quality leads to unreliable results of any kind of data processing and has profound economic impact. Although there are tools to help users with the task of data cleansing, support for dealing with the specifics of time-oriented data is rather poor. However, the time dimension has very specific characteristics which introduce quality problems, that are different from other kinds of data. We present TimeCleanser, an interactive Visual Analytics system to support the task of data cleansing of time-oriented data. In order to help the user to deal with these special characteristics and quality problems, TimeCleanser combines semi-automatic quality checks, visualizations, and directly editable data tables. The evaluation of the TimeCleanser system within a focus group (two target users, one developer, and two Human Computer Interaction experts) shows that (a) our proposed method is suited to detect hidden quality problems of time-oriented data and (b) that it facilitates the complex task of data cleansing.

Analysing Interactivity in Information Visualisation

Modern information visualisation systems do not only support interactivity but also increasingly complex problem solving. In this study we compare two interactive information visualisation systems: VisuExplore and Gravi++. By analysing logfiles we were able to identify sets of activities and interaction patterns users followed while working with these systems. These patterns are an indication of strategies users adopt to find solutions. Identifying such patterns may help in improving the design of future information visualisation systems.

Evaluating an InfoVis Technique Using Insight Reports

The evaluation of Information Visualization (InfoVis) techniques can help to identify specific strengths and weaknesses of these methods. The following article describes the results of an empirical study assessing the contribution of an interactive InfoVis method based on a spring metaphor (GRAVI), exploratory data analysis (EDA) and machine learning (ML) to ease understanding. The application domain is the psychotherapeutic treatment of anorectic young women. The three methods are supposed to support the therapists in finding the variables which influence success or failure of the therapy. To conduct the evaluation we developed a report system which helped subjects to formulate and document in a self-directed manner the insights they gained when using the three methods. The results indicate that the three methods are complementary and should be used in conjunction.

Pep Up Your Time Machine: Recommendations for the Design of Information Visualizations of Time-Dependent Data

Representing time-dependent data plays an important role in information visualization. Time presents specific challenges for the representation of data because time is a complex and highly abstract concept. Basically, there are two ways to support reasoning about time: time can be represented by space, and time can also be represented by time (animation). From the point of view of the users, both forms of representation have their strengths and weaknesses which we will illustrate in this chapter. In recent years, a large number of visualizations has been developed to solve the problem of representing time-dependent data. Nevertheless, it is still not clear which types of visualizations support the cognitive processes of the users. It is necessary to investigate the interactions of real users with visualizations to clarify this issue. The following chapter will give an overview of empirical evaluations and recommendations for the design of visualizations for time-dependent data.

Hypertext authoring and visualization

Visualizing information structure plays an increasing role in hypertext systems. Empirical evidence shows that such visualizations support the users or readers of hypertext systems. The following study investigates whether such information visualizations in the form of two-dimensional graphical overview maps also support the writers of hypertext documents. It also seems plausible to assume that the process of writing text changes when graphical overview maps integrated into hypertext systems are used. We also analysed the relationship between the authoring process and the character of the finished documents. In general, it can be said that visualizing the information structure inherent in a document plays an important role in hypertext authoring. It was the only innovative feature of the hypertext authoring system we developed which was used intensively by almost all the authors. In contrast to that, the finished documents were rather traditional. Authors did not exploit the novel features of hypertext/hypermedia systems like, e.g. introducing pictures, movies or sounds. On the basis of the analysis of the hypertext authoring process guidelines can be formulated to support writers of hypertext documents.

Patient development at a glance: an evaluation of a medical data visualization

This paper describes the results of an evaluation study of a prototype for the visualization of time-oriented medical data. Subjects were nine physicians. The prototype combines well-known visual representation techniques and extensive interaction techniques. The aim of the study was to assess the systems usability and whether the prototype solved relevant problems of physicians in hospitals. It was found that one of the great advantages of the system was that it allowed physicians to see the development of the patients at one glance. It was also shown that users clearly preferred an easy to learn and understand design and familiar visualizations.

Animation for Time-oriented Data: An Overview of Empirical Research

The usage of visualizations to aid the analysis of time oriented data plays an important role in various fields of applications. The need to visualize such data was decisive for the development of different visualization techniques over the last years. One of the frequently applied techniques is animation in order to illustrate the movements in such a way to make changes in the data transparent. However, evaluation studies of such animated interfaces for time-oriented data with potential users are still difficult to find. In this paper, we present our observations based on a systematic literature review with the motivation to support researchers and designers to identify future directions for their research. The literature review is split in two parts: (1) research on animation from the field of psychology, and (2) evaluation studies with the focus on animation of time-oriented data.