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  negligible and the speed-up considerable.  Exact computations can be
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  negligible and the speed-up considerable.  Exact computations can be
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  ensured by setting \code{delta} to a negative value.
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  ensured by setting \code{delta} to a negative value.
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  If \code{transform.pars} is true, the optimization is done using an
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  If \code{transform.pars} is true, the optimization is done using an
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  alternative parametrization which is a variation on that suggested by
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  alternative parametrization which is a variation on that suggested by
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  Jones (1980) and ensures that the model is stationary.  For an AR(p)
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  \bibcitet{R:Jones:1980} and ensures that the model is stationary.
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  For an AR(p)
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  model the parametrization is via the inverse tanh of the partial
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  model the parametrization is via the inverse tanh of the partial
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  autocorrelations: the same procedure is applied (separately) to the
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  autocorrelations: the same procedure is applied (separately) to the
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  AR and seasonal AR terms.  The MA terms are also constrained to be
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  AR and seasonal AR terms.  The MA terms are also constrained to be
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  invertible during optimization by the same transformation if
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  invertible during optimization by the same transformation if
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  \code{transform.pars} is true.  Note that the MLE for MA terms does
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  \code{transform.pars} is true.  Note that the MLE for MA terms does