© 1976 by Biometrika Trust
Miscellanea |
On two convex autocorrelation regions for moving average processes
Civil Service College London
The set of autocorrelations
, for MA(q), the general moving average process of order q, is considered, as a point in q-space. It is shown that the range of all such points is a convex region, which is a one-to-one map of the domain consisting of the sete of parameter points
, corresponding to all invertible and borderline noninvertible MA.(q) processes. It is also shown how an MA(q) process can be decomposed into a set of independent first-order seasonal moving average processes, provided that its set of autocorrelations is contained in a certain hypercubic subrange of the convex region.
Key Words: Borderline noninvertibility Fejér-Riesz theorem General autoregressive-moving average process Invertibility Rayleigh mapping Seasonal process Spectral density function