基于多维投影的社交网络可视化分析
Multidimensional Projections for Visual Analysis of Social Networks
-
摘要: 社交网络的可视化分析通常基于绘图算法和工具。 然而,社交网络是一种特殊的图,对图中显示关系的解释严重依赖于上下文。而上下文由与图中元素,如各个节点、边缘、边缘组合相关的属性以及个体间的联系性质来确定。除了获取基于强制布局策略的权重,在图布局的过程中,大多数系统都没有考虑个体和团体的属性。本文基于属性和连接映射,提出一套新的展示和探索社交网络的工具。通过多维投影技术,这些属性被用来在平面上放置节点。对于属性映射,我们表明在布局中节点邻近性对应属性的相似性,因此可以更加容易地定位具有相似属性的节点群。基于连接性的投影产生一个初始放置,放弃了基于强制或图分析算法,可以一次性获得一个有意义的布局。当强制算法被进一步应用到这一初始映射时,最终的布局呈现了比传统的基于强制方法更好的属性。数值评价显示了使用投影的预映射点的几个优点。用户评价表明,这些工具提升了操作的便利,加快了概念和关联的快速识别,获得单独利用传统的图可视化不易表达的效果。为了更好地便于复杂的网络空间使用,本文还实现了球体表面上的图形映射。Abstract: Visual analysis of social networks is usually based on graph drawing algorithms and tools. However, social networks are a special kind of graph in the sense that interpretation of displayed relationships is heavily dependent on context. Context, in its turn, is given by attributes associated with graph elements, such as individual nodes, edges, and groups of edges, as well as by the nature of the connections between individuals. In most systems, attributes of individuals and communities are not taken into consideration during graph layout, except to derive weights for force-based placement strategies. This paper proposes a set of novel tools for displaying and exploring social networks based on attribute and connectivity mappings. These properties are employed to layout nodes on the plane via multidimensional projection techniques. For the attribute mapping, we show that node proximity in the layout corresponds to similarity in attribute, leading to easiness in locating similar groups of nodes. The projection based on connectivity yields an initial placement that forgoes force-based or graph analysis algorithm, reaching a meaningful layout in one pass. When a force algorithm is then applied to this initial mapping, the final layout presents better properties than conventional force-based approaches. Numerical evaluations show a number of advantages of pre-mapping points via projections. User evaluation demonstrates that these tools promote ease of manipulation as well as fast identification of concepts and associations which cannot be easily expressed by conventional graph visualization alone. In order to allow better space usage for complex networks, a graph mapping on the surface of a sphere is also implemented.