Throws an error if the covariance structure of model_basic isn't the same
as or a special case of the covariance structure of model_augmented.
h_check_cov_struct_nesting(model_basic, model_augmented)"identical" if model_basic and model_augmented have the same
covariance structure. "nesting" if the covariance structure of
model_basic is a special case of the covariance structure of
model_augmented.
(mmrm_tmb_formula_parts)
the
formula_parts element of an mmrm model fit.
The check for "nesting" is a check against a mathematically determined hierarchy of the available cov_types: if restricting an aspect of a covariance structure can result in another covariance structure, the latter structure is nested within the former structure.
For upstream coding brevity, this function accepts the formula_parts
element of two mmrm model fits rather than mmrm objects. Such objects are
of class mmrm_tmb_formula_parts.