Finding the Plateau in an Aggregated Time Series

Given d input time series, an aggregated series can be formed by aggregating the d values at each time position. It is often useful to find the time positions whose aggregated values are the greatest. Instead of looking for individual top-k time positions, this paper gives two algorithms for finding the time interval (called the plateau) in which the aggregated values are close to each other (within a given threshold) and are all no smaller than the aggregated values outside of the interval. The first algorithm is a centralized one assuming that all data are available at a central location, and the other is a distributed search algorithm that does not require such a central location. The centralized algorithm has a linear time complexity with respect to the length of the time series, and the distributed algorithm employs the Threshold Algorithm by Fagin et al. and is quite efficient in reducing the communication cost as shown by the experiments reported in the paper.