Sigma parameterization for simple models

!TAU

!TAU} f specifies that \ASReml save any regression coefficient associated with covariate f as a string named Tau so that the value can be used to adjust data in the same run. For example, the following code a two stage analysis properly adjusting for plant height.

!ARG 1 2
adjusted variety means with weights  !DOPART \$1
  yield    plantheight    variety *
  row * column *
  adjyld !=plantheight !*\$Tau !*-1 !+yield
!skip 1   !Tau plantheight

1
~ mu plantheight mv !r variety
ar1(row).ar1(column)

2
-1 !HOLD !CONTINUE !MAXIT 1
~  mu variety mv
ar1(row).ar1(column)
variety !TWOSTAGE

This job fits two models. In the first pass, $Tau has a value of 1 when used to calculate adjyld but adjyld is not used in the first model. The coefficient value is updated at the end of the the first model fit to the regression coefficient obtained in that fit for plantheight. In the second model, we analyse adjyld which has been corrected for plantheight. To adjust to a particular value of plant height (say 1.4) rather than to plant height zero, adjyld should be defined as adjyld !=plantheight !-1.4 !*$Tau !*-1 !+yield

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