Dear all,
In the SASmixed package there is an example of an analysis of a split-plot experiment. The model is

  fm1Semi <- lme( resistance ~ ET * position, data = Semiconductor, random = ~ 1 | Grp)

where Grp in the Semiconductor dataset is defined as ET*Wafer. Is it possible to specify the grouping directly some way, e.g. like 

  fm1Semi <- lme( resistance ~ ET * position, data = Semiconductor, random = ~ 1 | ET*Wafer)

(this does not work, I know, but somehow I would expect it to be possible to get around having to define a new variable in the dataset)...

Thanks in advance
Søren Højsgaard

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