Andre Suslik Spritzer

A physics-based approach for interactive manipulation of graph visualizations

This paper presents an interactive physics-based technique for the exploration and dynamic reorganization of graph layouts that takes into account semantic properties which the user might need to emphasize. Many techniques have been proposed that take a graph as input and produce a visualization solely based on its topology, seldom ever relying on the semantic attributes of nodes and edges. These automatic topology-based algorithms might generate aesthetically interesting layouts, but they neglect information that might be important for the user. Among these are the force-directed or energy minimization algorithms, which use physics analogies to produce satisfactory layouts. They consist of applying forces on the nodes, which move until the physical system enters a state of mechanical equilibrium. We propose an extension of this metaphor to include tools for the interactive manipulation of such layouts. These tools are comprised of magnets, which attract nodes with user-specified criteria to the regions surrounding the magnets. Magnets can be nested and also used to intuitively perform set operations such as union and intersection, becoming thus an intuitive visual tool for sorting through the datasets. To evaluate the technique we discuss how they can be used to perform common graph visualization tasks.

Design and Evaluation of MagnetViz—A Graph Visualization Tool

MagnetViz was designed for the interactive manipulation of force-directed graph layouts, allowing the user to obtain visualizations based on the graph topology and/or the attributes of its nodes and edges. The user can introduce virtual magnets anywhere in the graph and these can be set to attract nodes and edges that fulfill user-defined criteria. When a magnet is placed, the force-directed nature of the layout forces it to reorganize itself in order to reflect the changes in the balance of forces, consequently changing the visualization into one that is more semantically relevant to the user. This paper describes MagnetVizs concepts, illustrating them with examples and a case study based on a usage scenario. We also describe how the MagnetViz has evolved since its original version and present the evaluation of its latest version. This evaluation consists of two user studies aiming at assessing generated layout quality and how well the concepts can be apprehended and employed, and a task taxonomy assessment focusing on establishing which graph visualization tasks the technique is able to handle.

Towards a smooth design process for static communicative node-link diagrams

Node‐link infographics are visually very rich and can communicate messages effectively, but can be very difficult to create, often involving a painstaking and artisanal process. In this paper we present an investigation of node‐link visualizations for communication and how to better support their creation. We begin by breaking down these images into their basic elements and analyzing how they are created. We then present a set of techniques aimed at improving the creation workflow by bringing more flexibility and power to users, letting them manipulate all aspects of a node‐link diagram (layout, visual attributes, etc.) while taking into account the context in which it will appear. These techniques were implemented in a proof‐of‐concept prototype called GraphCoiffure, which was designed as an intermediary step between graph drawing/editing software and image authoring applications. We describe how GraphCoiffure improves the workflow and illustrate its benefits through practical examples.

A visual tool to support technical analysis of stock market data

A stock market investor relies on two schools of analysis of market behavior to determine a trading strategy: Technical Analysis and Fundamental Analysis. Fundamental Analysis is based on the study of the fundamental data of a company and more directed to long-term investments, not taking into account small short-term price oscillations. On the other hand, Technical Analysis is mostly used for mid and short-term investments and is based on the study of past price behavior through the use of statistical tools and price history charts, taking into consideration the hypothesis that prices form patterns and reflect all the relevant information about a company and about the psychology of other investors. The application of Technical Analysis requires a computational system capable of displaying price history charts and providing tools to be used with them. This paper presents a prototype for a portable, extensible and easy-to-use tool for desktop/laptop and handheld computers that provides the investor with techniques for the visualization of stock market data. Classical visualization techniques and tools, such as Line, Bar, Candlestick and Point and Figure Charts, as well as extra tools, such as candlestick pattern recognition, are available as built-in functions, but new tools and visualizations can be easily added. The software was built with the .NET and .NET Compact frameworks and utilizes XML to store the data set.

Balancing User Interaction and Control in BNSL

In this paper we present a study based on an evolutionary framework to explore what would be a reasonable compromise between interaction and automated optimisation in finding possible solutions for a complex problem, namely the learning of Bayesian network structures, an NP-hard problem where user knowledge can be crucial to distinguish among solutions of equal fitness but very different physical meaning. Even though several classes of complex problems can be effectively tackled with Evolutionary Computation, most possess qualities that are difficult to directly encode in the fitness function or in the individual’s genotype description. Expert knowledge can sometimes be used to integrate the missing information, but new challenges arise when searching for the best way to access it: full human interaction can lead to the well-known problem of user-fatigue, while a completely automated evolutionary process can miss important contributions by the expert. For our study, we developed a GUI-based prototype application that lets an expert user guide the evolution of a network by alternating between fully-interactive and completely automatic steps. Preliminary user tests were able to show that despite still requiring some improvements with regards to its efficiency, the proposed approach indeed achieves its goal of delivering satisfying results for an expert user.