ASReml-S reference manual - VSN International

3.16 Testing of terms: the wald() method 35units in which the data are ordered traits within units. An algebraic expression for thevariance matrix in this case isI n ⊗ Σwhere Σ (n t ×n t ) is an unstructured variance matrix.For a standard multivariate analysis• the error structure must be specified as two-dimensional, with independent units andoften an unstructured variance matrix across traits.– the rcov this model is therefore rcov ∼ units:us(trait)– missing values are allowed and must be fitted. asreml automatically includes thespecial factor mv in the sparse formula in such cases.• for the default analysis, that is the response is specified as a matrix, the R structuremust reflect the data order of traits within units which means that the term unitsmust appear before trait in the rcov formula.• variance parameters are variances, not variance ratios.• the error structure is often specified as an unstructured variance matrix but correlationmodels may also be used. asreml attempts to detect such cases and fix or estimatethe residual scale parameter accordingly.For example, with the Wolfinger data the times are equally spaced so we could fit afirst order autoregressive model using:> wolfinger.asr