Learning temporal causal structures among multiple time series is one of the major tasks in mining time series data. Granger causality is one of the most popular techniques in uncovering the temporal dependencies among time series; however it faces two main challenges: (i) the spurious effect of unobserved time series and (ii) the computational challenges in high dimensional settings. In this paper, we utilize the confounder path delays to find a subset of time series that via conditioning on them we are able to cancel out the spurious confounder effects. After study of consistency of different Granger causality techniques, we propose Copula-Granger and show that while it is consistent in high dimensions, it can efficiently capture non-linearity in the data. Extensive experiments on a synthetic and a social networking dataset confirm our theoretical results.
IntroductionIn the era of data deluge, we are confronted with largescale time series data, i.e., a sequence observations of concerned variables over a period of time. For example, terabytes of neural activity time series data are produced to record the collective response of neurons to different stimuli; petabytes of climate and meteorological data, such as temperature, solar radiation, and precipitation, are collected over the years; and exabytes of social media contents are generated over time on the Internet. A major data mining task for time series data is to uncover the temporal causal relationship among the time series. For example, in the climatology, we want to identify the factors that impact the climate patterns of certain regions. In social networks, we are interested in identification of the patterns of influence among users and how topics activate or suppress each other. Developing effective and scalable data mining algorithms to uncover temporal dependency structures between time series and reveal insights from data has become a key problem in machine learning and data mining.There are two major challenges in discovering temporal causal relationship in large-scale data: (i) not all influential confounders are observed in the datasets and