# Subsetting a factor

## !SUBSET

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.
#### Example

!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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