Mathieu Jacomy

ForceAtlas2, a Continuous Graph Layout Algorithm for Handy Network Visualization Designed for the Gephi Software

Gephi is a network visualization software used in various disciplines (social network analysis, biology, genomics…). One of its key features is the ability to display the spatialization process, aiming at transforming the network into a map, and ForceAtlas2 is its default layout algorithm. The latter is developed by the Gephi team as an all-around solution to Gephi users’ typical networks (scale-free, 10 to 10,000 nodes). We present here for the first time its functioning and settings. ForceAtlas2 is a force-directed layout close to other algorithms used for network spatialization. We do not claim a theoretical advance but an attempt to integrate different techniques such as the Barnes Hut simulation, degree-dependent repulsive force, and local and global adaptive temperatures. It is designed for the Gephi user experience (it is a continuous algorithm), and we explain which constraints it implies. The algorithm benefits from much feedback and is developed in order to provide many possibilities through its settings. We lay out its complete functioning for the users who need a precise understanding of its behaviour, from the formulas to graphic illustration of the result. We propose a benchmark for our compromise between performance and quality. We also explain why we integrated its various features and discuss our design choices.

Narrating Networks : Exploring the affordances of networks as storytelling devices in journalism

Networks have become the de facto diagram of the Big Data age (try searching Google Images for [big data AND visualisation] and see). The concept of networks has become central to many fields of human inquiry and is said to revolutionise everything from medicine to markets to military intelligence. While the mathematical and analytical capabilities of networks have been extensively studied over the years, in this article we argue that the storytelling affordances of networks have been comparatively neglected. In order to address this we use multimodal analysis to examine the stories that networks evoke in a series of journalism articles. We develop a protocol by means of which narrative meanings can be construed from network imagery and the context in which it is embedded, and discuss five different kinds of narrative readings of networks, illustrated with analyses of examples from journalism. Finally, to support further research in this area, we discuss methodological issues that we encountered and suggest directions for future study to advance and broaden research around this defining aspect of visual culture after the digital turn.

Actor-Network VS Network Analysis VS Digital Networks Are We Talking About the Same Networks?

Este artigo discute diferencas e afinidades entre tres tipos de rede (Ator-Rede, Analise de Redes e Redes Digitais) importantes para o Digital STS. 2 Nas ultimas decadas, a colonizacao de pesquisas em STS foi lenta e gradual. Ela se inicia com a Teoria Ator-Rede (TAR), que oferece um conjunto de nocoes para descrever a construcao de fenomenos sociotecnicos. Com o advento da Analise de Redes, estudiosos incorporam tecnicas de investigacao e visualizacao desenvolvidas pela Analise de Redes Sociais (ARS) e pela Cientometria aos estudos em STS. Com o crescente uso de recursos computacionais pelos STS, estudiosos atentam para as Redes Digitais como modo de rastrear a vida coletiva. Muitos pesquisadores tentaram relacionar esses tres movimentos aos metodos digitais, ao apostarem que a TAR pode ser operacionalizada por meio da Analise de Redes, gracas aos dados providos pelas Redes Digitais. No entanto, alem da homonimia presente na palavra “rede”, que caracteriza as tres abordagens mencionadas, ha poucas evidencias que comprovam a continuidade entre esses tres tipos de rede. Falamos das mesmas redes?

How to Tell Stories with Networks: Exploring the Narrative Affordances of Graphs with the Iliad

The chapter starts with a short summary of what we consider to be five central challenges concerning the recent move towards Digital Methods. We then interrogate David Berry’s concept of ‘digital Bildung’ as a means of facing these challenges. Our goal in this discussion is, maybe paradoxically, to move the spotlight from ‘the digital’ and programming, to the plethora of concepts and knowledges mobilized in digital tools. To this end, we discuss three examples that allow us to both concretise and complicate the debate about what kind of skill set is needed by digital scholars.