随着图规模的增大,传统的力导引布局算法会出现节点重叠、边交叉等视觉混乱问题,为此提出一种基于改进力导引布局的可扩展的可视化层级抽象方法.首先结合FR算法与LinLog算法的优点对力导引算法进行改进,生成一个具有明显聚类结构、能够体现图结构信息的初步布局;然后基于布局结果,采用自下而上的层次聚类方法生成图的层级结构,同时定义了体现抽象层级的参数来决定不同层级下的聚类显示,允许用户在多个层级观察数据结构特征;最后采用几何距离、拓扑结构和拓扑结构加中介中心性3种不同的度量进行视觉抽象,并对抽象结果进行比较分析.为了说明文中方法的有效性,分别对信息可视化文章间的文献引用数据、2004年美国总统竞选的政治博客数据,以及IEEE Visualization会议文章的作者合作数据这3个数据实例进行实验,结果表明,使用该方法并结合移动、缩放、选择等可视化交互技术,能有效地帮助用户分析、探索和理解数据隐藏的信息.%With the increase of graph size, there appears visual clutter for the traditional force directed layout al-gorithms, such as node overlapping and edge crossing. Aiming to address this problem, a scalable hierarchical visual abstraction method based on improved force directed layout is proposed. We first combine the advantages of FR algorithm and LinLog algorithm to improve the force directed algorithm, which generates the preliminary layout for graphs with clear clustering structures. Based on this layout results, a bottom-up hierarchical clustering method is used to generate the graph's hierarchical structure. We define the parameter of abstraction levels to de-termine the clustering under different hierarchies, so that the users can observe the graph layout structures at mul-tiple levels. Finally, we use three different metrics, which are Euclidean geometric distance, topological structure based distance and topological distance adding betweenness centrality, to compute the visual abstractions. The corresponding layout abstractions are compared and analyzed. In order to illustrate the effectiveness of the pro-posed method, three real-world datasets are visualized and analyzed in our experiments. The three datasets are ci-tation data of information visualization papers, the political blog data for the 2004 US presidential campaign and the co-author data from the IEEE Visualization conference. The experimental results show that combining the visual interactive technologies such as panning, zooming and selecting, our method can help users to analyze, ex-plore and understand the hidden information of the data effectively.
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