This is an S3 generic. See, e.g. `PCMDefaultObject.MatrixParameter`.
PCMDefaultObject(spec, model, ...)
any object having a class attribute. The value of this object is not used, but its class is used for method-dispatch.
a PCM object used to extract attributes needed for creating a
default object of class specified in class(spec)
, such as the number of
traits (k) or the regimes and the number of regimes;
additional arguments that can be used by methods.
a parameter or a PCM object.