EFFECT Statement

EFFECT name = effect-type ( variables </ options> ) ;

The EFFECT statement enables you to construct special collections of columns for design matrices. These collections are referred to as constructed effects to distinguish them from the usual model effects formed from continuous or classification variables, as discussed in the section GLM Parameterization of Classification Variables and Effects of Chapter 19, Shared Concepts and Topics.

The following effect-types are available:


is a collection effect that defines one or more variables as a single effect with multiple degrees of freedom. The variables in a collection are considered as a unit for estimation and inference.


is a classification effect in which the level that is used for a given period corresponds to the level in the preceding period.

Note: The LAG effect-type is experimental in this release.


is a multimember classification effect whose levels are determined by one or more variables that appear in a CLASS statement.


is a multivariate polynomial effect in the specified numeric variables.


is a regression spline effect whose columns are univariate spline expansions of one or more variables. A spline expansion replaces the original variable with an expanded or larger set of new variables.

Table 87.2 summarizes important options for each type of EFFECT statement.

Table 87.2 Important EFFECT Statement Options



Options for Collection Effects


Displays the constituents of the collection effect

Options for Lag Effects


Names a variable that controls to which lag design an observation is assigned


Displays the lag design of the lag effect


Specifies the number of periods in the lag


Names the variable that defines the period


Names the variable or variables that define the group within which each period is defined

Options for Multimember Effects


Specifies that observations with all missing levels for the multimember variables should have zero values in the corresponding design matrix columns


Specifies the weight variable for the contributions of each of the classification effects

Options for Polynomial Effects


Specifies the degree of the polynomial


Specifies the maximum degree of any variable in a term of the polynomial


Specifies centering and scaling suboptions for the variables that define the polynomial

Options for Spline Effects


Specifies the type of basis (B-spline basis or truncated power function basis) for the spline expansion


Specifies the degree of the spline transformation


Specifies how to construct the knots for spline effects

For further details about the syntax of these effect-types and how columns of constructed effects are computed, see the section EFFECT Statement of Chapter 19, Shared Concepts and Topics.