ASReml-S reference manual - VSN International

4.2 A sequence of structures for the NIN field trial data 40• Using a separable model for the R structure implies that the data can be regardedas a matrix or array whose data is indexed by the levels of the factors that representthe rows and columns of this array. In this field trial example these factors are Rowand Column, respectively. For this structure to be applicable, the data in this casemust be augmented with 18 additional missing values. Variety is arbitrarily coded asLANCER for all of the extra missing plots• asreml automatically includes missing values in the sparse component with a factornamed mv(see Section 3.12).• unlike G structures, asreml automatically includes and estimates θ. In this examplethe variance models specified for Row (ar1()) and Column (default id()) are correlationmodels. If the R structure is a variance matrix then the parameter θ must beconstrained to 1.0 (using the dispersion argument to the appropriate family function,such as asreml.gaussian()). asreml attempts to detect these situations but it is wise toexplicitly constrain θ. Specifically, the call> sp.asr sp.asr sp.asr sp.asr