José Fernando Rodrigues

Frequency plot and relevance plot to enhance visual data exploration

We present two techniques aiming at exploring databases through multivariate visualizations. Both techniques intend to deal with the problem caused by the limited amount of elements that can be presented simultaneously in traditional visual exploration procedures. The first technique, the Frequency Plot, combines data frequency with interactive filtering to identify clusters and trends in subsets of the database. Thus, graphical elements (lines, pixels, icons, or graphical marks) are color differentiated proportionally to how frequent the value being represented is, while interactive filtering allows the selection of interesting partitions of the database. The second technique, the Relevance Plot, corresponds to assigning different levels of color distinguishably to visual elements according to their relevance to a users specified data properties set, which can be chosen visually and dynamically.

Reviewing Data Visualization: an Analytical Taxonomical Study

This paper presents an analytical taxonomy that can suitably describe, rather than simply classify, techniques for data presentation. Unlike previous works, we do not consider particular aspects of visualization techniques, but their mechanisms and foundational vision perception. Instead of just adjusting visualization research to a classification system, our aim is to better understand its process. For doing so, we depart from elementary concepts to reach a model that can describe how visualization techniques work and how they convey meaning

BoWFire: Detection of Fire in Still Images by Integrating Pixel Color and Texture Analysis

Emergency events involving fire are potentially harmful, demanding a fast and precise decision making. The use of crowd sourcing image and videos on crisis management systems can aid in these situations by providing more information than verbal/textual descriptions. Due to the usual high volume of data, automatic solutions need to discard non-relevant content without losing relevant information. There are several methods for fire detection on video using color-based models. However, they are not adequate for still image processing, because they can suffer on high false-positive results. These methods also suffer from parameters with little physical meaning, which makes fine tuning a difficult task. In this context, we propose a novel fire detection method for still images that uses classification based on color features combined with texture classification on super pixel regions. Our method uses a reduced number of parameters if compared to previous works, easing the process of fine tuning the method. Results show the effectiveness of our method of reducing false-positives while its precision remains compatible with the state-of-the-art methods.

Combining Visual Analytics and Content Based Data Retrieval Technology for Efficient Data Analysis

One of the most useful techniques to help visual data analysis systems is interactive filtering (brushing). However, visualization techniques often suffer from overlap of graphical items and multiple attributes complexity, making visual selection inefficient. In these situations, the benefits of data visualization are not fully observable because the graphical items do not pop up as comprehensive patterns. In this work we propose the use of content-based data retrieval technology combined with visual analytics. The idea is to use the similarity query functionalities provided by metric space systems in order to select regions of the data domain according to user-guidance and interests. After that, the data found in such regions feed multiple visualization workspaces so that the user can inspect the correspondent datasets. Our experiments showed that the methodology can break the visual analysis process into smaller problems (views) and that the views hold the expectations of the analyst according to his/her similarity query selection, improving data perception and analytical possibilities. Our contribution introduces a principle that can be used in all sorts of visualization techniques and systems, this principle can be extended with different kinds of integration visualization-metric-space, and with different metrics, expanding the possibilities of visual data analysis in aspects such as semantics and scalability.

The spatial-perceptual design space: a new comprehension for data visualization

We revisit the design space of visualizations aiming at identifying and relating its components. In this sense, we establish a model to examine the process through which visualizations become expressive for users. This model has lead us to a taxonomy oriented to the human visual perception. The essence of this taxonomy provides natural criteria in order to delineate a novel understanding for the design space of visualizations. From such understanding, we elaborate a model for generalized design. The model poses an intuitive comprehension for the visualization design space departing from fundamental pre-attentive stimuli and from perceptual phenomena. The paper is presented as a survey, its structure introduces an alternative conceptual organization for the space of techniques concerning visual analysis.

On the convergence of nanotechnology and Big Data analysis for computer-aided diagnosis

An overview is provided of the challenges involved in building computer-aided diagnosis systems capable of precise medical diagnostics based on integration and interpretation of data from different sources and formats. The availability of massive amounts of data and computational methods associated with the Big Data paradigm has brought hope that such systems may soon be available in routine clinical practices, which is not the case today. We focus on visual and machine learning analysis of medical data acquired with varied nanotech-based techniques and on methods for Big Data infrastructure. Because diagnosis is essentially a classification task, we address the machine learning techniques with supervised and unsupervised classification, making a critical assessment of the progress already made in the medical field and the prospects for the near future. We also advocate that successful computer-aided diagnosis requires a merge of methods and concepts from nanotechnology and Big Data analysis.

Local descriptors for soybean disease recognition

A novel approach is proposed for soybean disease recognition using leaf images.It is based on local descriptors and bag-of-visual words.Experimental results on an image dataset with 1200 samples validate its effectiveness.Results also show that color increases the correct classification rate. The detection of diseases is of vital importance to increase the productivity of soybean crops. The presence of the diseases is usually conducted visually, which is time-consuming and imprecise. To overcome these issues, there is a growing demand for technologies that aim at early and automated disease detection. In this line of work, we introduce an effective (over 98% of accuracy) and efficient (an average time of 0.1s per image) method to computationally detect soybean diseases. Our method is based on image local descriptors and on the summarization technique Bag of Visual Words. We tested our approach on a dataset composed of 1200 scanned soybean leaves considering healthy samples, and samples with evidence of three diseases commonly observed in soybean crops - Mildew, Rust Tan, and Rust RB. The experimental results demonstrated the accuracy of the proposed approach and suggested that it can be easily applied to other kinds of crops.

Learning Profile Identification Based on the Analysis of the User's Context of Interaction

One of the e-learning environment goal is to attend the individual needs of students during the learning process. The adaptation of contents, activities and tools into different visualization or in a variety of content types is an important feature of this environment, bringing to the user the sensation that there are suitable workplaces to his profile in the same system. Nevertheless, it is important the investigation of student behaviour aspects, considering the context where the interaction happens, to achieve a efficient personalization process. The paper goal is to present an approach to identify the student learning profile analyzing the context of interaction. Besides this, the learning profile could be analized in different dimensions allows the system to deal with the different focus of the learning.

Supervised-learning link recommendation in the DBLP co-authoring network

Currently, link recommendation has gained more attention as networked data becomes abundant in several scenarios. However, existing methods for this task have failed in considering solely the structure of dynamic networks for improved performance and accuracy. Hence, in this work, we present a methodology based on the use of multiple topological metrics in order to achieve prospective link recommendations considering time constraints. The combination of such metrics is used as input to binary classification algorithms that state whether two pairs of authors will/should define a link. We experimented with five algorithms, what allowed us to reach high rates of accuracy and to evaluate the different classification paradigms. Our results also demonstrated that time parameters and the activity profile of the authors can significantly influence the recommendation. In the context of DBLP, this research is strategic as it may assist on identifying potential partners, research groups with similar themes, research competition (absence of obvious links), and related work.

Graph-Based Relational Data Visualization

Relational databases are rigid-structured data sources characterized by complex relationships among a set of relations (tables). Making sense of such relationships is a challenging problem because users must consider multiple relations, understand their ensemble of integrity constraints, interpret dozens of attributes, and draw complex SQL queries for each desired data exploration. In this scenario, we introduce a twofold methodology, we use a hierarchical graph representation to efficiently model the database relationships and, on top of it, we designed a visualization technique for rapidly relational exploration. Our results demonstrate that the exploration of databases is deeply simplified as the user is able to visually browse the data with little or no knowledge about its structure, dismissing the need for complex SQL queries. We believe our findings will bring a novel paradigm in what concerns relational data comprehension.