Anisotropic Radial Layout for Visualizing Centrality and Structure in Graphs

This paper presents a novel method for layout of undirected graphs, where nodes (vertices) are constrained to lie on a set of nested, simple, closed curves. Such a layout is useful to simultaneously display the structural centrality and vertex distance information for graphs in many domains, including social networks. Closed curves are a more general constraint than the previously proposed circles, and afford our method more flexibility to preserve vertex relationships compared to existing radial layout methods. The proposed approach modifies the multidimensional scaling (MDS) stress to include the estimation of a vertex depth or centrality field as well as a term that penalizes discord between structural centrality of vertices and their alignment with this carefully estimated field. We also propose a visualization strategy for the proposed layout and demonstrate its effectiveness using three social network datasets.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Gravity-Inspired Graph Autoencoders for Directed Link Prediction

Graph autoencoders (AE) and variational autoencoders (VAE) recently emerged as powerful node embedding methods. In particular, graph AE and VAE were successfully leveraged to tackle the challenging link prediction problem, aiming at figuring out whether some pairs of nodes from a graph are connected by unobserved edges. However, these models focus on undirected graphs and therefore ignore the potential direction of the link, which is limiting for numerous real-life applications. In this paper, we extend the graph AE and VAE frameworks to address link prediction in directed graphs. We present a new gravity-inspired decoder scheme that can effectively reconstruct directed graphs from a node embedding. We empirically evaluate our method on three different directed link prediction tasks, for which standard graph AE and VAE perform poorly. We achieve competitive results on three real-world graphs, outperforming several popular baselines.Comment: ACM International Conference on Information and Knowledge Management (CIKM 2019

Fast filtering and animation of large dynamic networks

Detecting and visualizing what are the most relevant changes in an evolving network is an open challenge in several domains. We present a fast algorithm that filters subsets of the strongest nodes and edges representing an evolving weighted graph and visualize it by either creating a movie, or by streaming it to an interactive network visualization tool. The algorithm is an approximation of exponential sliding time-window that scales linearly with the number of interactions. We compare the algorithm against rectangular and exponential sliding time-window methods. Our network filtering algorithm: i) captures persistent trends in the structure of dynamic weighted networks, ii) smoothens transitions between the snapshots of dynamic network, and iii) uses limited memory and processor time. The algorithm is publicly available as open-source software.Comment: 6 figures, 2 table

Customer churn prediction in telecom using machine learning and social network analysis in big data platform

Customer churn is a major problem and one of the most important concerns for large companies. Due to the direct effect on the revenues of the companies, especially in the telecom field, companies are seeking to develop means to predict potential customer to churn. Therefore, finding factors that increase customer churn is important to take necessary actions to reduce this churn. The main contribution of our work is to develop a churn prediction model which assists telecom operators to predict customers who are most likely subject to churn. The model developed in this work uses machine learning techniques on big data platform and builds a new way of features' engineering and selection. In order to measure the performance of the model, the Area Under Curve (AUC) standard measure is adopted, and the AUC value obtained is 93.3%. Another main contribution is to use customer social network in the prediction model by extracting Social Network Analysis (SNA) features. The use of SNA enhanced the performance of the model from 84 to 93.3% against AUC standard. The model was prepared and tested through Spark environment by working on a large dataset created by transforming big raw data provided by SyriaTel telecom company. The dataset contained all customers' information over 9 months, and was used to train, test, and evaluate the system at SyriaTel. The model experimented four algorithms: Decision Tree, Random Forest, Gradient Boosted Machine Tree "GBM" and Extreme Gradient Boosting "XGBOOST". However, the best results were obtained by applying XGBOOST algorithm. This algorithm was used for classification in this churn predictive model.Comment: 24 pages, 14 figures. PDF https://rdcu.be/budK

Construindo grafos de conhecimento utilizando documentos textuais para análise de literatura científica

Orientador: Julio Cesar dos ReisDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: O número de publicações científicas que pesquisadores tem que ler vem aumento nos últimos anos. Consequentemente, dentre várias opções, é difícil para eles identificarem documentos relevantes relacionados aos seus estudos. Ademais, para entender como um campo científico é organizado, e para estudar o seu estado da arte, pesquisadores geralmente se baseiam em artigos de revisão de uma área. Estes artigos podem estar indisponíveis ou desatualizados dependendo do tema estudado. Usualmente, pesquisadores têm que realizar esta árdua tarefa de pesquisa fundamental manualmente. Pesquisas recentes vêm desenvolvendo mecanismos para auxiliar outros pesquisadores a entender como campos científicos são estruturados. Entretanto, estes mecanismos são focados exclusivamente em recomendar artigos relevantes para os pesquisadores ou os auxiliar em entender como um ramo da ciência é organizado ao nível de publicação. Desta forma, estes métodos limitam o entendimento sobre o ramo estudado, não permitindo que interessados estudem os conceitos e relações abstratas que compõe um ramo da ciência e as suas subáreas. Esta dissertação de mestrado propõe um framework para estruturar, analisar, e rastrear a evolução de um campo científico no nível dos seus conceitos. Ela primeiramente estrutura o campo científico como um grafo-de-conhecimento utilizando os seus conceitos como vértices. A seguir, ela automaticamente identifica as principais subáreas do campo estudado, extrai as suas frases-chave, e estuda as suas relações. Nosso framework representa o campo científico em diferentes períodos do tempo. Esta dissertação compara estas representações, e identifica como as subáreas do campo estudado evoluiram no decorrer dos anos. Avaliamos cada etapa do nosso framework representando e analisando dados científicos provenientes de diferentes áreas de conhecimento em casos de uso. Nossas descobertas indicam o sucesso em detectar resultados similares em diferentes casos de uso, indicando que nossa abordagem é aplicável à diferentes domínios da ciência. Esta pesquisa também contribui com uma aplicação com interface web para auxiliar pesquisadores a utilizarem nosso framework de forma gráfica. Ao utilizar nossa aplicação, pesquisadores podem ter uma análise geral de como um campo científico é estruturado e como ele evoluiAbstract: The amount of publications a researcher must absorb has been increasing over the last years. Consequently, among so many options, it is hard for them to identify interesting documents to read related to their studies. Researchers usually search for review articles to understand how a scientific field is organized and to study its state of the art. This option can be unavailable or outdated depending on the studied area. Usually, they have to do such laborious task of background research manually. Recent researches have developed mechanisms to assist researchers in understanding the structure of scientific fields. However, those mechanisms focus on recommending relevant articles to researchers or supporting them in understanding how a scientific field is organized considering documents that belong to it. These methods limit the field understanding, not allowing researchers to study the underlying concepts and relations that compose a scientific field and its sub-areas. This Ms.c. thesis proposes a framework to structure, analyze, and track the evolution of a scientific field at a concept level. Given a set of textual documents as research papers, it first structures a scientific field as a knowledge graph using its detected concepts as vertices. Then, it automatically identifies the field's main sub-areas, extracts their keyphrases, and studies their relations. Our framework enables to represent the scientific field in distinct time-periods. It allows to compare its representations and identify how the field's areas changed over time. We evaluate each step of our framework representing and analyzing scientific data from distinct fields of knowledge in case studies. Our findings indicate the success in detecting the sub-areas based on the generated graph from natural language documents. We observe similar outcomes in the different case studies by indicating our approach applicable to distinct domains. This research also contributes with a web-based software tool that allows researchers to use the proposed framework graphically. By using our application, researchers can have an overview analysis of how a scientific field is structured and how it evolvedMestradoCiência da ComputaçãoMestre em Ciência da Computação2013/08293-7 ; 2017/02325-5FAPESPCAPE