Subsetting a factor


This qualifier provides a convenient way to define a new version of a factor with a subset of the levels of an existing factor.
     !SUBSET name factor subset
definitions occur as separate lines between the datafile line and the model line.
     name is the name of the model term being defined.
     factor is the name of an existing factor.
     subset is the list of factor levels to include in the new factors.


 !SUBSET  EnvC  Env  3 5 8 9 :15 21 33
defines model term EnvC which is a factor of 12 (since there are 12 elements in the list), being a reduced form of the factor Env just selecting the environments listed. It might be used in the model in an interaction to fit say column effects for the nominated environments. The intention is to simplify the model specification in MET (Multi Environment Trials). Missing values are transmitted as missing and records whose level is zero are transmitted as zero.

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