  Multivariate time-series forecasting plays a crucial role in many real-world
applications. It is a challenging problem as one needs to consider both
intra-series temporal correlations and inter-series correlations
simultaneously. Recently, there have been multiple works trying to capture both
correlations, but most, if not all of them only capture temporal correlations
in the time domain and resort to pre-defined priors as inter-series
relationships.
  In this paper, we propose Spectral Temporal Graph Neural Network (StemGNN) to
further improve the accuracy of multivariate time-series forecasting. StemGNN
captures inter-series correlations and temporal dependencies \textit{jointly}
in the \textit{spectral domain}. It combines Graph Fourier Transform (GFT)
which models inter-series correlations and Discrete Fourier Transform (DFT)
which models temporal dependencies in an end-to-end framework. After passing
through GFT and DFT, the spectral representations hold clear patterns and can
be predicted effectively by convolution and sequential learning modules.
Moreover, StemGNN learns inter-series correlations automatically from the data
without using pre-defined priors. We conduct extensive experiments on ten
real-world datasets to demonstrate the effectiveness of StemGNN. Code is
available at https://github.com/microsoft/StemGNN/
