| complex_vs {asreml} | R Documentation |
Variance structure spanning several model terms
Description
General variance structure specifying a set of terms to be included in the random argument that collectively will have an associated variance model.
Usage
str(form, vmodel)
Arguments
form |
A model formula included verbatim in the |
vmodel |
A direct product variance model for the set of terms given in
|
Details
Typically, a variance structure applies to an individual term (main effect or interaction) in the linear model, and there is no covariance between random model terms. Sometimes it is appropriate to include a covariance, such as random coefficients regression. In such cases it is essential that the model terms be contiguous and that the variance structure defined is the structure required across all terms in the set.
The model terms in form are consequently not reordered.
While asreml
will check the overall size of the included terms, it cannot check
that the order of effects matches the structure definition in
vmodel; care must be taken to ensure this is correct. Check
that the terms are conformable by considering the order of the
fitted effects and ensuring the first term of the direct product in
vmodel corresponds to the outer factor in the nesting of the
effects in form.