A Bayesian approach is presented for estimating a mixture of linear Gaussia
n stale space models. Such models are used to model interventions in time s
eries and nonparametric regression. Markov chain Monte Carlo sampling is us
ually necessary to obtain the posterior distributions of such mixture model
s, because it is difficult to obtain them analytically. The methodological
contribution of the article is to derive a set of recursions for dynamic mi
xture models that efficiently implement a Markov chain Monte Carlo sampling
scheme that converges rapidly to the posterior distribution. The methodolo
gy is illustrated by fitting an autoregressive model subject to interventio
ns to zinc concentration in sludge.