Research On Problems Of Network Simplification By Edge Bundling

Visualization is an important method of apperceiving and analyzing network information, but with the increment of network scale and complexity, visual clutter problems like node occlusion and edge congestion emerges. Simplifying network to reduce the difficulty in apperceiving the link pattern and inner structure becomes main task for network visualization researchers to solve.The paper lays emphasis on edge bundling technique through edge convergence, and bundle edges close to each other in network to reduce visual complexity. A segmental FDA simplification model and a group based edge consistent edge bundling model of network are proposed and improved, the evaluation by user study is scheduled for the models. The main innovation and contribution lists as below:First, the paper proposes and improves two edge bundling models in visualizing network. To solve the visual clutter problem in network, edges close to each other in network are bundled by curving them and the bundling starts from node position and group division. In segmental FDA bundling model, quadratic spline is used to display line in network, control points of spline are produced by iteration and implement edge bundling. To solve the problem of excessive bending of some edges in segmental FDA bundling model, network is divided into different groups by CNM cluster algorithm. Lines in the same group are applied edge consistent principle on basement of network group structure, and bundling level is calculated by the matching coefficient of edges. After edge bundling, the phenomena of curve’s distortion decreases and curves become smoother. The bundling simplification algorithm introduced in this essay has a wide applicability, and network visualized by this method has pleasing visual effect and readability.Second, an evaluation method is proposed to verify the simplification effect of two edge bundling models introduced before, the evaluation consists of network’s statistical indicators and user test. To evaluate the network diagram quality, a method which combines visual analysis, network statistical indicators analysis and user test is put forward. Bundling simplified network is compared and analyzed from aspects like node centrality, node betweenness centrality, group structure, visual cluster and link pattern. Evaluating airline network diagram drawn by the simplification model is done by establishing two tasks and choosing volunteers. The evaluation results impersonally reveal that simplification model introduced can reduce visual clutter, and make topology structure and nodes’ connection characteristics more clear.Third, the group structure and connection pattern is found in airline network on the basement of this method. In this essay, domestic airline network data is chosen as experimental subject, and simplify the network by two bundling model, and then analyze the simplification result. Experimental result shows that group structure of domestic airport can be divided into four groups, and positions of nodes in the same group stand close to each other; airline network shows distinct crossing skeleton, airlines having north-south orientation and west-east orientation bundle independently, which reveals the whole trends of airline network construction in two directions; high degree nodes connect to each other across regions, and display strong bundle characteristic in north-south orientation, and node connections across regions develops in hinging pattern, on the other hand, the airlines bundle less in west-east orientation, and node connections across regions develop in dispersing pattern.