(Received January 4, 1993; revised February 4, 1994)
Abstract. A Gaussian-sum smoother is developed based on the two filter formula for smoothing. This facilitates the application of non-Gaussian state space modeling to diverse problems in time series analysis. It is especially useful when a higher order state vector is required and the application of the non-Gaussian smoother based on direct numerical computation is impractical. In particular, applications to the non-Gaussian seasonal adjustment of economic time series and to the modeling of seasonal time series with several outliers are shown.
Key words and phrases: Non-Gaussian smoother, non-Gaussian filter, Gaussian mixture, nonstationary time series, outliers, seasonal adjustment.