Mapping change in large networks
(July 2009)Abstract
Change is a fundamental ingredient of interaction patterns in biology, technology, the economy, and science itself: Interactions within and between organisms change; transportation patterns by air, land, and sea all change; the global nancial
ow changes; and the frontiers of scienti c research change. Networks and clustering methods have become important tools to comprehend instances of these large-scale structures, but without methods to distinguish between real trends and noisy data, these approaches are not useful for studying how networks change. Only if we can assign signi cance to the partition of single networks can we distinguish meaningful structural changes from random
uctuations. Here we show that bootstrap resampling accompanied by signi cance clustering provides a solution to this problem. To be able to connect changing structures with the changing function of networks, we highlight and summarize the signi cant structural changes with alluvial diagrams and realize de Solla Price's vision of mapping change in science: studying the citation pattern between about 7000 scienti c journals over the past decade, we nd that neuroscience has transformed from an interdisciplinary specialty to a mature and stand-alone discipline.