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6 Command file: Specifying the terms in the mixed model 89Sparse fixed termsThe !f sparse fixed terms in model formula• are the fixed covariates (for example, thefixed lin(row) covariate now included inthe model formula), factors and interactionsincluding special functions and reservedwords (for example mv, see Table6.1) for which ANOVA type tests are notrequired,• include large (>100 levels) terms.NIN Alliance Trial 1989variety.row 22column 11nin89.asd !skip 1yield ∼ mu variety !r repl,!f mv lin(row)1 211 column AR1 .42422 row AR1 .9046.4 Random terms in the modelThe !r random terms in the model formula• comprise random covariates, factors and interactionsincluding special functions andreserved words, see Table 6.1,• involve an initial non-zero variance componentor ratio (relative to the residual variance)default 0.1; the initial value can bespecified after the model term or if the variancestructure is not scaled identity, by syntaxdescribed in detail in Chapter 7,NIN Alliance Trial 1989variety.row 22column 11nin89.asd !skip 1yield ∼ mu variety !r repl,!f mv 1 211 column AR1 .42422 row AR1 .904• an initial value of its variance (ratio) may be followed by a !GP (keep positive,the default), !GU (unrestricted) or !GF (fixed) qualifier, see Table 7.4,• use !{ and !} to group model terms that may not be reordered. NormallyASReml will reorder the model terms in the sparse equations - putting smallerterms first to speed up calculations. However, the order must be preserved if theuser defines a structure for a term which also covers the following term(s) (a wayof defining a covariance structure across model terms). Grouping is specificallyrequired if the model terms are of differing sizes (number of effects). Forexample, for traits weaning weight and yearling weight, an animal modelwith maternal weaning weight should specify model terms!{ Trait.animal at(Trait,1).dam !}when fitting a genetic covariance between the direct and maternal effects.