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arXiv 1809.09602stat.ME
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稀疏动态网络的最优变点检测与定位

Optimal Change Point Detection and Localization in Sparse Dynamic Networks

Daren Wang, Yi Yu, Alessandro Rinaldo

摘要:

研究了动态网络模型中的变点定位问题。我们假设我们观察到一系列相同大小的独立邻接矩阵,每个对应于一个未知的非齐次伯努利模型的实现。邻接矩阵的基本分布是分段恒定的,并且可以在称为变化点的时间点的子集上改变。我们关心的是恢复未知数量和位置的变化点。在我们的模型设置中,我们允许所有模型参数随时间点的总数而变化,包括网络大小,连续变化点之间的最小间距,最小变化的幅度和网络的稀疏程度。我们首先确定一个区域的不可能性在空间中的模型参数,使得没有变点估计是可证明的一致的,如果数据是根据参数落在该区域。我们提出了一个计算简单的算法网络变点定位,称为网络二进制分割,依赖于加权平均的邻接矩阵。我们表明,网络二进制分割是一致的模型参数的范围内,几乎涵盖了补充的不可能区域,从而证明了存在的相变的问题。接下来,我们设计了一个更复杂的算法的基础上奇异值阈值,称为局部细化,提供更准确的估计的变化点的位置。在适当的条件下,局部精化保证了一个最小最大的最优率的网络变点定位,同时保持计算可行。

英文摘要:

We study the problem of change point localization in dynamic networks models. We assume that we observe a sequence of independent adjacency matrices of the same size, each corresponding to a realization of an unknown inhomogeneous Bernoulli model. The underlying distribution of the adjacency matrices are piecewise constant, and may change over a subset of the time points, called change points. We are concerned with recovering the unknown number and positions of the change points. In our model setting we allow for all the model parameters to change with the total number of time points, including the network size, the minimal spacing between consecutive change points, the magnitude of the smallest change and the degree of sparsity of the networks. We first identify a region of impossibility in the space of the model parameters such that no change point estimator is provably consistent if the data are generated according to parameters falling in that region. We propose a computationally-simple algorithm for network change point localization, called Network Binary Segmentation, that relies on weighted averages of the adjacency matrices. We show that Network Binary Segmentation is consistent over a range of the model parameters that nearly cover the complement of the impossibility region, thus demonstrating the existence of a phase transition for the problem at hand. Next, we devise a more sophisticated algorithm based on singular value thresholding, called Local Refinement, that delivers more accurate estimates of the change point locations. Under appropriate conditions, Local Refinement guarantees a minimax optimal rate for network change point localization while remaining computationally feasible.

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