• Separate the effects with spaces .

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• Use a vertical bar ( | ) to create main effects and interactions. For example, A|B|C is the same as A B A*B C A*C B*C A*B*C .

• Use an at-sign ( @ ) following the use of vertical bars to remove interaction terms. For example, A|B|C@2 removes the three-way interaction term from A|B|C .