MTS2Graph: Interpretable multivariate time series classification with temporal evolving graphs

Conventional time series classification approaches based on bags of patterns or shapelets face significant challenges in dealing with a vast amount of feature candidates from high-dimensional multivariate data. In contrast, deep neural networks can learn low-dimensional features efficiently, and in particular, convolutional neural networks have shown promising results in classifying multivariate time series data. A key factor in the success of deep neural networks is this astonishing expressive power. However, this power comes at the cost of complex, black-boxed models, conflicting with the goals of building reliable and human-understandable models. In this work1, we introduce a new interpretable framework for multivariate time series data that by extracting and clustering the input quantifies the contribution of time-varying input variables and each signal's role to the classification. We construct a graph that captures the temporal relationship between the extracted patterns for each layer and propose an effective merging strategy to aggregate those graphs into one. Finally, a graph embedding algorithm generates new representations of the created interpretable time-series features. Our extensive experiments indicate the benefit of our time-aware graph-based representation in multivariate time series classification while enriching them with more interpretability.