Model functions


units creates a factor with a level for every record in the data file. This is used to fit the 'nugget' variance when a correlation structure is applied to the residual.

uni() function

uni(f,k[,n]) creates a factor with a level for every record subject to the factor level of f equalling k, i.e. a new level is created for the factor whenever a new record is encountered whose integer truncated data value from data field f is k. Thus uni(site,2) would be used to create an independent error term for site 2 in a multi-environment trial and is equivalent to at(site,2).units. The default size of this model term is the number of data records. The user may specify a lower number as the third argument. There is little computational penalty from the default but the .sln file may be substantially larger than needed.

uni(f[,0[,n]]) creates a factor with a new level whenever there is a level present for the factor f. Levels (effects) are not created if the level of factor f is 0, missing or negative. The size may be set in the third argument by setting the second argument to zero.

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