Estimation in time series with an unknown number of deterministic trigonometric components with unknown amplitudes and frequencies is considered. A stepwise procedure is used. At each step the frequency of the largest term in the periodogram of the residual series is used as a starting value for finding the best frequency in the least squares sense. The procedure is stopped when there are no further significant harmonic components, when tested by a multiple-test procedure. The fitting procedure is tried on various time series, including the sun-spot series. For long-term prediction the deterministic model does better for the sunspot series than, for example, autoregressive models.
No takes yet. Share an insight, caveat, or question.
Damsleth et al. (1982) studied this question.