Adding Terms to a Cox Regression Model

When requesting a custom model, you can add terms to the model by clicking the Add new model terms button on the Model tab. A new dialog box opens in which you can specify terms.

Type of term to add. There are several ways to add terms to the model, based on the selection of input fields in the Available fields list.

Single interaction. Inserts the term representing the interaction of all selected fields.
Main effects. Inserts one main effect term (the field itself) for each selected input field.
All 2-way interactions. Inserts a 2-way interaction term (the product of the input fields) for each possible pair of selected input fields. For example, if you have selected input fields A, B, and C in the Available fields list, this method will insert the terms A * B, A * C, and B * C.
All 3-way interactions. Inserts a 3-way interaction term (the product of the input fields) for each possible combination of selected input fields, taken three at a time. For example, if you have selected input fields A, B, C, and D in the Available fields list, this method will insert the terms A * B * C, A * B * D, A * C * D, and B * C * D.
All 4-way interactions. Inserts a 4-way interaction term (the product of the input fields) for each possible combination of selected input fields, taken four at a time. For example, if you have selected input fields A, B, C, D, and E in the Available fields list, this method will insert the terms A * B * C * D, A * B * C * E, A * B * D * E, A * C * D * E, and B * C * D * E.

Available fields. Lists the available input fields to be used in constructing model terms. Note that the list may include fields that are not legal input fields, so take care to ensure that all model terms include only input fields.

Preview. Shows the terms that will be added to the model if you click Insert, based on the selected fields and the term type selected above.

Insert. Inserts terms in the model (based on the current selection of fields and term type) and closes the dialog box.