Argument model is used as a template to specify values of
parameters and/or which parameters to estimate or fix. In general,
If a value of a parameter in model is NA, then it is to
be estimated. Otherwise the parameter is taken as is.
The current implementation is incomplete. In particular, the AR
parameters are always designated for estimation.
Argument shift can be used to overwrite some or values
component shift in model. If shift has length
one, it is replicated to the number of MixAR components. If
shift[k] is TRUE, then the shift coefficient for the
k-th component is set to NA to request its
estimation. Otherwise, the value of the shift for the k-th component
in model is taken.
Argument shift has a default of TRUE which causes the
shift coefficients to be estimated irrespectively of their values in
model.
est_templ returns a list with as many components as there are
MixAR components in the model. The k-th component of the list is itself a list
specifing which parameters of the i-th MixAR component to estimate or fix.