The visualization of hierarchically structured data over time is an ongoing challenge and several approaches exist trying to solve it. Techniques such as animated or juxtaposed tree visualizations are not capable of providing a good overview of the time series and lack expressiveness in conveying changes over time. Nested streamgraphs provide a better understanding of the data evolution, but lack the clear outline of hierarchical structures at a given timestep. Furthermore, these approaches are often limited to static hierarchies or exclude complex hierarchical changes in the data, limiting their use cases. We propose a novel visual metaphor capable of providing a static overview of all hierarchical changes over time, as well as clearly outlining the hierarchical structure at each individual time step. Our method allows for smooth transitions between treemaps and nested streamgraphs, enabling the exploration of the trade-off between dynamic behavior and hierarchical structure. As our technique handles topological changes of all types, it is suitable for a wide range of applications. We demonstrate the utility of our method on several use cases, evaluate it with a user study, and provide its full source code.

中文翻译：

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SplitStreams：不断发展的层次结构的视觉隐喻

随着时间的推移分层结构化数据的可视化是一个持续的挑战，有几种方法试图解决它。动画或并列树可视化等技术无法提供时间序列的良好概览，并且在传达随时间变化的变化方面缺乏表现力。嵌套流图提供了对数据演变的更好理解，但缺乏给定时间步长层次结构的清晰轮廓。此外，这些方法通常仅限于静态层次结构或排除数据中复杂的层次结构变化，从而限制了它们的用例。我们提出了一种新颖的视觉隐喻，能够提供所有层次随时间变化的静态概览，并清楚地概述每个时间步长的层次结构。我们的方法允许树图和嵌套流图之间的平滑过渡，从而能够探索动态行为和层次结构之间的权衡。由于我们的技术处理所有类型的拓扑变化，因此适用于广泛的应用。我们在几个用例中演示了我们的方法的实用性，通过用户研究对其进行了评估，并提供了其完整的源代码。