EuroVisShort2018

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https://diglib.eg.org/handle/10.2312/2632400

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Evolutionary Lines for Flow Visualization
(The Eurographics Association, 2018) Engelke, Wito; Hotz, Ingrid; Jimmy Johansson and Filip Sadlo and Tobias Schreck
In this work we explore evolutionary algorithms for selected a visualization application. We demonstrate its potential using an example from flow visualization showing promising first results. Evolutionary algorithms, as guided search approach, find close-to-optimal solutions with respect to some fitness function in an iterative process using biologically motivated mechanisms like selection, mutation and recombination. As such, they provide a powerful alternative to filtering methods commonly used in visualization where the space of possible candidates is densely sampled in a pre-processing step from which the best candidates are selected and visualized. This approach however tends to be increasingly inefficient with growing data size or expensive candidate computations resulting in large pre-processing times. We present an evolutionary algorithm for the problem of streamline selection to highlight features of interest in flow data. Our approach directly optimizes the solution candidates with respect to a user selected fitness function requiring significantly less computations. At the same time the problem of possible under-sampling is solved since we are not tied to a preset resolution. We demonstrate our approach on the well-known flow around an obstacle as case with a two-dimensional search space. The blood flow in an aneurysm serves as an example with a three-dimensional search space. For both, the achieved results are comparable to line filtering approaches with much less line computations.
TapVis: A Data Visualization Approach for Assessment of Alternating Tapping Performance in Patients with Parkinson's Disease
(The Eurographics Association, 2018) Jusufi, Ilir; Memedi, Mevludin; Nyholm, Dag; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Advancements in telemedicine have been helpful for frequent monitoring of patients with Parkinson's disease (PD) from remote locations and assessment of their individual symptoms and treatment-related complications. These data can be useful for helping clinicians to interpret symptom states and individually tailor the treatments by visualizing the physiological information collected by sensor-based systems. In this paper we present a visualization metaphor that represents symptom information of PD patients during tapping tests performed with a smartphone. The metaphor has been developed and evaluated with a clinician. It enabled the clinician to observe fine motor impairments and identify motor fluctuations regarding several movement aspects of patients that perform the tests from their homes.
Pixel Wise Pie Charts: Placement of Data Points Visualizing Spatial Value Distributions
(The Eurographics Association, 2018) Janetzko, Halldor; Stein, Manuel; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Handling overplotted points in spatial pixel-based visualizations is usually done either by aggregation or sampling. The third rather unusual alternative is replacing data items untangling overplotted regions. Depending on the placement algorithm visual artifacts will be created based on an optimization between overplotting, display usage, and conservation. In this paper, we exploit the replacement and create pixel-based pie-charts reflecting the numerical distribution of spatially referenced data points. With this novel approach, we bridge the gap between the overview and detail phase in Shneiderman's Information Seeking mantra. Our presented algorithm is informally evaluated with a biological case study on baboon movement.
Visualizing Functional Regions by Analysis of Geo-textual Data
(The Eurographics Association, 2018) Wang, Yunzhe; Baciu, George; Li, Chenhui; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Using tremendous geo-textual data collected from social media applications, we facilitate the analysis of region functions. By extracting semantics from textual properties, we aim at classifying geographical locations in terms of their functional types. Hence, we train a classification model with the Support Vector Machine, and apply it to aggregated word embeddings to predict the function of spots. We highly cooperate with techniques in graph analysis. Firstly, regions are segmented based on a latent graph. Then, we propose an adaptive layout solution to deal with situations of multi-AOI queries. The generated layout and interactive metaphor provide convenience for observation and comparison. Experiments are conducted with the YFCC100M dataset to prove the effectiveness of our system.
Risk Fixers and Sweet Spotters: a Study of the Different Approaches to Using Visual Sensitivity Analysis in an Investment Scenario
(The Eurographics Association, 2018) Torsney-Weir, Thomas; Afroozeh, Shahrzad; Sedlmair, Michael; Möller, Torsten; Jimmy Johansson and Filip Sadlo and Tobias Schreck
We present an empirical study that illustrates how individual users' decision making preferences and biases influence visualization design choices. Twenty-three participants, in a lab study, were shown two interactive financial portfolio optimization interfaces which allowed them to adjust the return for the portfolio and view how the risk changes. One interface showed the sensitivity of the risk to changes in the return and one did not have this feature. Our study highlights two classes of users. One which preferred the interface with the sensitivity feature and one group that does not prefer the sensitivity feature. We named these two groups the ''risk fixers'' and the ''sweet spotters'' due to the analysis method they used. The ''risk fixers'' selected a level of risk which they were comfortable with while the ''sweet spotters'' tried to find a point right before the risk increased greatly. Our study shows that exposing the sensitivity of investment parameters will impact the investment decision process and increase confidence for these ''sweet spotters.'' We also discuss the implications for design.
Exploring Interactive Linking Between Text and Visualization
(The Eurographics Association, 2018) Latif, Shahid; Liu, Diao; Beck, Fabian; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Visualizations are included in documents as augmentation to text and they become more intuitive if readers have the ability to interact with them. Modern web technologies facilitate the development of interactive documents including both text and visualizations. The aim of this research it to explore the design space of possible visualization-text linking and interactions based on various triggers such as mouse events. We describe a framework that takes text containing markup, a related dataset, and a configuration file as inputs and produces an interactive document. The resulting document provides interactions such as details on demand, visual highlighting and comparison, and bushing-and-linking. In addition to regular sized graphics, the use of word-sized graphics or sparklines presents related content in view-focus of the reader. Finally, an illustrative example is presented to showcase the approach.
STEIN: Speeding up Evaluation Activities With a Seamless Testing Environment INtegrator
(The Eurographics Association, 2018) Angelini, Marco; Blasilli, Graziano; Lenti, Simone; Santucci, Giuseppe; Jimmy Johansson and Filip Sadlo and Tobias Schreck
The evaluation of an information visualization system is a complex activity, involving the understanding of both the visualization itself and the process that it is meant to support. Moreover, if the evaluation activity includes a task based user study, it requires a considerable effort, involving both conceptual (e.g., the definition of user tasks) and technical (e.g., logging of the relevant user actions while using the system) aspects. The solution presented in this paper, STEIN (Seamless Testing Environment INtegrator), allows integrating the system under evaluation with the questions that have been designed for the user study, tracing the user's activities and automatically collecting the user's answers using the events that are generated while interacting with the system. This results in a substantial reduction of the effort associated with technical activities, thus allowing the evaluation designer to focus mainly on the conceptual aspects. A prototype of the system is available for download at awareserver.dis.uniroma1.it:8080/stein.
VisGuides: A Forum for Discussing Visualization Guidelines
(The Eurographics Association, 2018) Diehl, Alexandra; Abdul-Rahman, Alfie; El-Assady, Mennatallah; Bach, Benjamin; Keim, Daniel; Chen, Min; Jimmy Johansson and Filip Sadlo and Tobias Schreck
This paper presents VisGuides, a discussion platform to facilitate the collection, evaluation, critique, revision, and dissemination of visualization guidelines. As visualization becomes a more widespread discipline with much more attention by designers and the general public, we need to ensure mechanisms for communicating, transferring, and accessing visualization knowledge. A visualization guideline can be anything ranging from good practices, empirical studies, and survey reports with the goal to inform visualization design and understanding. Thus, our forum aims (i) to collect visualization guidelines, (ii) to discuss guidelines and collect respective empirical references, and in the long run, (iii) to establish formal knowledge about guidelines by analyzing the forum content and the consensus of discussions. This paper describes the VisGuides forum and outlines our preliminary research towards shedding more light on visualization guidelines. VisGuides is accessible online at visguides.org.
Using a Task Classification in the Visualisation Design Process for Task Understanding and Abstraction: an Empirical Study
(The Eurographics Association, 2018) Kerracher, Natalie; Kennedy, Jessie B.; Chalmers, Kevin; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Task classifications are widely purported to be useful in the design process, with various suggestions having been made for their use at the different stages. However, little has been written regarding the actual use of task classifications in these design scenarios or reflection on the success (or otherwise) of employing them in this respect. In this paper we explore the use of a task classification at the task understanding and abstraction stages of the design process. Specifically, we use a task classification to overcome some of the known problems of eliciting tasks from domain experts during requirements gathering and as a lexicon for task abstraction. Our initial findings suggest that using a task classification helps domain experts to articulate tasks which they may not otherwise have identified. Using a task classification for task abstraction allowed us to characterise tasks in a consistent manner and organise them to establish the most commonly occurring and important tasks.
Visual Analysis of Parallel Interval Events
(The Eurographics Association, 2018) Qi, Ji; Liu, Cong; Cappers, B. C. M. (Bram); Wetering, Huub van de; Jimmy Johansson and Filip Sadlo and Tobias Schreck
System logs typically contain lines with time stamps that each describes an event. Where these events semantically form start and end events, they can be combined into interval events. For visual event analytics, the analysis of interval events is more complex than that of point events, since not only the order of events, but also temporal overlaps have to be taken into account. To address this increased complexity and for the purpose of system understanding and analysis, we present SELE, a domainindependent tool for visualizing parallel interval events. SELE is intended to be used on a single long trace of events. A visual technique named strata timeline is developed to handle visual scalability issues. Finally, a multi-core parallel graph searching algorithm is analyzed to demonstrate SELE.
DiffPin: Interactive Specification of References for Comparative Small-Multiple Displays
(The Eurographics Association, 2018) Spechtenhauser, Florian; Piringer, Harald; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Small-multiple displays are frequently used for visual comparison by juxtaposition. Explicitly encoding differences between cells enables to convey also minor differences in the data, but requires to specify references for the comparison which is non-trivial in views with a complex layout. This paper proposes DiffPin - an interaction technique to flexibly specify references for cells in small-multiple views. DiffPin enables an easy and fast specification of references on different levels of the visualization (e.g. cell, row, column), even in complex small-multiple views containing nested axes or subtotals. The paper provides considerations for visual encodings in comparative small-multiple displays using DiffPin, and proposes strategies for visually discriminating reference data from compared data for specific visualization types. Initial qualitative user feedback indicates that users are intuitively able to use the provided interactions to quickly and efficiently perform comparative tasks.
Improving Provenance Data Interaction for Visual Storytelling in Medical Imaging Data Exploration
(The Eurographics Association, 2018) Amabili, Lorenzo; Kosinka, Jiri; Meersbergen, Maarten A. J. van; Ooijen, Peter M. A. van; Roerdink, Jos B. T. M.; Svetachov, Pjotr; Yu, Lingyun; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Effective collaborative work in diagnostic medical imaging is not trivial due to the large amounts of complex data involved, a (non-linear) workflow involving experts in different domains, and a lack of versatility in the current tools employed in healthcare. In this paper, we aim to introduce how the integration of visual storytelling techniques together with provenance data in the analytic systems used in medicine can compensate for these issues, by enhancing communication of results and reproducibility of findings through diagnostic provenance data. To this end, we illustrate how we can improve the interaction with provenance data displayed in a graph in order to facilitate authoring and the creation process of visual data stories.
Issues and Suggestions for the Development of a Biodiversity Data Visualization Support Tool
(The Eurographics Association, 2018) Kaur, Pawandeep; Klan, Friederike; König-Ries, Birgitta; Jimmy Johansson and Filip Sadlo and Tobias Schreck
Visualizations are an important tool to transport information. However, finding the right visualization can be challenging. Using the biodiversity research domain as a showcase, we investigate where exactly these challenges are and what a tool should look like that helps scientists overcome them. Our results are based on a survey we performed.
Learning from the Best - Visual Analysis of a Quasi-Optimal Data Labeling Strategy
(The Eurographics Association, 2018) Bernard, Jürgen; Hutter, Marco; Lehmann, Markus; Müller, Martin; Zeppelzauer, Matthias; Sedlmair, Michael; Jimmy Johansson and Filip Sadlo and Tobias Schreck
An overarching goal of active learning strategies is to reduce the human effort when labeling datasets and training machine learning methods. In this work, we focus on the analysis of a (theoretical) quasi-optimal, ground-truth-based strategy for labeling instances, which we refer to as the upper limit of performance (ULoP). Our long-term goal is to improve existing active learning strategies and to narrow the gap between current strategies and the outstanding performance of ULoP. In an observational study conducted on five datasets, we leverage visualization methods to better understand how and why ULoP selects instances. Results show that the strategy of ULoP is not constant (as in most state-of-the-art active learning strategies) but changes within the labeling process. We identify three phases that are common to most observed labeling processes, partitioning the labeling process into (1) a Discovery Phase, (2) a Consolidation Phase, and (3) a Fine Tuning Phase.
Touch the Time: Touch-Centered Interaction Paradigms for Time-Oriented Data
(The Eurographics Association, 2018) Riehmann, Patrick; Reibert, Joshua; Opolka, Jens; Froehlich, Bernd; Jimmy Johansson and Filip Sadlo and Tobias Schreck
We present novel direct-touch centered paradigms for exploring time series data visualized in a coordinated multi-view display. The views can be easily and flexibly configured by choosing from various adapted or enhanced time-oriented visualizations. A vocabulary of robust direct-touch gestures enables the user to create, filter, derive, and focus on subsets of time-oriented data within the temporal dimension as well as the (data) records dimension. Our two-dimensional Focus&Context technique works particularly well with our extension to horizon graphs, which enables interactive scaling from area charts to multiply folded Horizon Graphs down to pixel-based visualizations and back.
EuroVis 2018 Short Papers: Frontmatter
(The Eurographics Association, 2018) Johansson, Jimmy; Sadlo, Filip; Schreck, Tobias; Jimmy Johansson and Filip Sadlo and Tobias Schreck
ChemoExplorer: A Dashboard for the Visual Analysis of Chemotherapy Response in Breast Cancer Patients
(The Eurographics Association, 2018) Karall, Nikolaus; Gröller, Eduard; Raidou, Renata Georgia; Jimmy Johansson and Filip Sadlo and Tobias Schreck
In breast cancer chemotherapy treatment, different alternative strategies can be employed. Clinical researchers working on the optimization of chemotherapy strategies need to analyze the progress of the treatment and to understand how different groups of patients respond to selected therapies. This is a challenging task, because of the multitude of imaging and non-imaging health record data involved. We, hereby, introduce a web-based dashboard that facilitates the comparison and analysis of publicly available breast cancer chemotherapy response data, consisting of a follow-up study of 63 patients. Each patient received one of two available therapeutic strategies and their treatment response was documented. Our dashboard provides an initial basis for clinical researchers working on chemotherapy optimization, to analyze the progress of treatment and to compare the response of (groups of) patients with distinct treatment characteristics. Our approach consists of multiple linked representations that provide interactive views on different aspects of the available imaging and non-imaging data. To illustrate the functionality of the ChemoExplorer, we conducted a usage scenario that shows the initial results of our work.
Pressure-based Vortex Extraction in Cardiac 4D PC-MRI Blood Flow Data
(The Eurographics Association, 2018) Köhler, Benjamin; Grothoff, Matthias; Gutberlet, Matthias; Preim, Bernhard; Jimmy Johansson and Filip Sadlo and Tobias Schreck
We propose a technique for vortex extraction in cardiac 4D PC-MRI blood flow data that employs an intravascular, relative pressure calculation. The method is easy to implement, runs fully automatically, and requires no user-defined parameters. We qualitatively evaluated 100+ datasets of the aorta, pulmonary artery, or left ventricle from healthy volunteers as well as from patients acquired with different MR scanners. In all cases, the results suffer from significantly less noise than comparable approaches using the common λ 2 vortex criterion.
Comparative Visual Analysis of Pelvic Organ Segmentations
(The Eurographics Association, 2018) Reiter, Oliver; Breeuwer, Marcel; Gröller, Eduard; Raidou, Renata Georgia; Jimmy Johansson and Filip Sadlo and Tobias Schreck
In prostate cancer treatment, automatic segmentations of the pelvic organs are often used as input to radiotherapy planning systems. However, natural anatomical variability of the involved organs is a common reason, for which segmentation algorithms fail, introducing errors in the radiotherapy treatment procedure, as well. Understanding how the shape and size of these organs affect the accuracy of segmentation is of major importance for developers of segmentation algorithms. However, current means of exploration and analysis provide limited insight. In this work, we discuss the design and implementation of a web-based framework, which enables easy exploration and detailed analysis of shape variability, and allows the intended users - i.e., segmentation experts - to generate hypotheses in relation to the performance of the involved algorithms. Our proposed approach was tested with segmentation meshes from a small cohort of 17 patients. Each mesh consists of four pelvic organs and two organ interfaces, which are labeled and have per-triangle correspondences. A usage scenario and an initial informal evaluation with a segmentation expert demonstrate that our framework allows the developers of the algorithms to quickly identify inaccurately segmented organs and to deliberate about the relation of variability to anatomical features and segmentation quality.
Perception-Aware Uncertainty Glyphs in the 3D Vector Fields
(The Eurographics Association, 2018) Lee, Joong-Youn; Park, Jinah; Jimmy Johansson and Filip Sadlo and Tobias Schreck
We often cannot avoid value uncertainties when curating raw data to obtain a final visualization image. Although numerous studies maintain the importance of uncertainty visualization, there lack a standard means of depicting the information, especially in 3D flow visualization tasks. We introduce a novel glyph design referred to as the disk-tailed arrow which shows the trends and uncertainties in 3D vector fields concisely. The proposed design includes a glyph shape and modeling strategies which map statistical information to visual cues. Our scheme is devised so that the user can perceive 3D uncertainty information effectively. We also present a case study of the application of the proposed glyph to an actual flow dataset as an assessment.

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