Anderson Gregorio Marques Soares

The Treemap is one of the most relevant information visualization (InfoVis) techniques to support the analysis of large hierarchical data structures or data clusters. Despite that, Treemap still presents some challenges for data representation, such as the few options for visual data mappings and the inability to represent zero and negative values. Additionally, visualizing high dimensional data requires many hierarchies, which can impair data visualization. Thus, this paper proposes to add layered glyphs to Treemap’s items to mitigate these issues. Layered glyphs are composed of N partially visible layers, and each layer maps one data dimension to a visual variable. Since the area of the upper layers is always smaller than the bottom ones, the layers can be stacked to compose a multidimensional glyph. To validate this proposal, we conducted a user study to compare three scenarios of visual data mappings for Treemaps: only Glyphs (G), Glyphs and Hierarchy (GH), and only Hierarchy (H). Thirty-six volunteers with a background in InfoVis techniques, organized into three groups of twelve (one group per scenario), performed 8 InfoVis tasks using only one of the proposed scenarios. The results point that scenario GH presented the best accuracy while having a task-solving time similar to scenario H, which suggests that representing more data in Treemaps with layered glyphs enriched the Treemap visualization capabilities without impairing the data readability.

Element overlap in visualization techniques is a known problem, and high amounts of data and lack of available visual space potentialize this issue. Many studies have applied techniques to reduce occlusion levels in data visualizations, such as random jitter, element transparency, layout rearrangement, and focus+context techniques. However, few studies focus on the presence of occlusion, which is a relevant topic for visualizations where some degree of overlap is inevitable or purposefully explored. This paper takes a step in this direction, and presents a comparative study of visual variables, measuring their robustness to overlap and number of unique values. The study used a grid layout to display visual variables (hue, saturation, shape, text, orientation, and texture), and varied percentage of occlusion (0%, 50%, 60% and 70%) and number of unique values (3, 4 and 5) to measure the effect they cause on the speed and accuracy to locate the visual variables. Hence, 48 volunteers performed locate tasks on a tool that automatically generate a grid of visual variables and collect their answers. The results revealed that hue and shape were robust to high occlusion levels and a high number of unique values. Text and texture had medium loss of performance, while saturation and orientation were the most negatively affected.

Treemap is one of the most well-known and used techniques for data analysis in InfoVis. However, it still presents some challenges concerning data representation, such as small items, a large number of hierarchies limiting the visual space, few options for visual data representation (restricted to size, color, label), and others. Thus, this paper presents an InfoVis tool that allows the analysis of multidimensional data using treemaps with glyphs, once they represent more data visually combined visual variables. Besides that, considering treemap scenarios with small area items, an algorithm was developed to analyze which part of the glyph the application should draw since parts of the glyph can still provide useful information. In this way, the glyphs become adaptative to available space. The application has a multilabel decision tree technique that decides which part of the glyph should appear. Visualization specialists supplied the training data through a system that showed a diverse range of glyphs' representations. The system varied the glyph's size, the number and the value of the visible visual variables and registered the response of specialists in the training data. Finally, this paper presents images using the treemap with adaptive glyphs approach versos treemap+glyphs and showed that the adaptive approach clears information clutter when treemap items are small.

Design and develop collaborative methods in information visualization are a current challenge, hence understand, identify and define the current progress of developed methods to collaborate in information visualization are important. The aim of this work is to review the ways and strategies of how to collaborate in information visualization applications. We surveyed published works that present applications that implements collaborative information visualization techniques and methods. We present a micro level category of identified ways of how the InfoVis applications implements collaboration.

Water is one of the main resources of nature, being the element directly related with maintenance of life in any ecosystem. For mankind, beside the biologic needs, water is used in many sectors of society, and one of them is electricity generation. For the full operation of hydroelectric power plants there is a need to create a huge water reservoir, which transforms the ecosystem and local economy, serving multiple uses, such as tourism, fishing, recreation, sailing, among others. The maintenance in this context is dependent of the quality of water in reservoir, which justifies its continuous monitoring. From the monitored data, it is possible to predict or classify the hydrologic cycle for the reservoir, aiming to support the process of decision about the hydric resources and environmental impact. Thus, this paper presents a practical approach to use visualization techniques based on the PRISMA software, which is a visualization tool with features of multiples views and coordinated databases to identify patterns in hydrologic cycles, considering the psycho-chemical elements existent in the dam water of the hydroelectric power plant from Tucuruí - Pará - Brazil.

This paper presents results of head tracker and speech commands interaction evaluation in information visualization context at low level task taxonomy. The head tracker is used to move a pointer and the voice commands to perform actions. In the evaluation, we used 20 public information visualization techniques, 62 simple tasks (aiming low-level interactions), and 10 participants performed all tasks. The evaluation shows results about user performance (UP) and user experience (UE) by visualization and interaction taxonomies. Finally, we highlight some good practices suggestions for design of this type of interaction.

The Internet has played an important role as a knowledge-sharing network and in this context some service oriented architecture (SOA) applications have emerged in all kind of study fields. Therefore, this work aims the design and development of a service aggregation that will favor ubiquity and pervasiveness in data visualization applications, allowing users to build domain-specific data visualizations in an easy and intuitive way. With this kind of service, it is possible to build data visualization applications for different smart devices such as smartphones, tablets, desktop, smart TV's, etc. A Web API that supports the main functionalities of an information visualization tool in different platforms has been proposed to reaches these purposes. The REST (Representational State Transfer) Style has been employed in the service conception as the architectural communication model. Client-side and server-side applications were developed using Java with a data visualization generator engine called PRISMA.

The current Brazilian context in television audiovisual communication is in transition from analogical to digital technology. One of the main reasons for this motion towards Interactive Digital Television (iDTV) is the improvement in the user experience over this platform. Considering this motion, this work applied suitable interaction design and usability concepts from the Nielsen's heuristics [5] into a visualization prototype to the support of visual analysis of products in electronic commerce over TV (t-commerce). In this work we conducted a usability check in an existing information visualization prototype, in order establish whether or not it follows usability standards and in order to make it more usable to the user.

Frequency-based statistical charts are the most widespread visualizations and the preferred of Infovis novices. They are important in depicting categorical data and providing data abstraction on large datasets. The drill down feature enables better visual scaling by allowing navigation through aggregation hierarchies. In this paper we discuss design considerations that impact on the usability in drill down charts. We develop a tool based on pie chart in order to illustrate the discussion. Moreover, we suggest visual representations and an interaction model. Finally, we provide evidence on the benefit of using such techniques for visual analysis of categorical data through a short usability study.