## DIRECT Statement

**DIRECT** * variables ***;**

The DIRECT statement lists numeric independent variables to
be treated in a quantitative, rather than qualitative, way.
The DIRECT statement is useful for logistic
regression, which is described in the "Logistic Regression" section.
For limitations of models involving continuous variables,
see the "Continuous Variables" section.
If specified, the DIRECT statement must precede the MODEL
statement. For example,

proc catmod;
direct X;
model Y=X;
run;

Suppose X has five levels. Then the main effect
X induces only one column in the design matrix, rather than
four. The values inserted into the design matrix are the
actual values of X.

You can interactively change the variables declared as
DIRECT variables by using the statement without listing any
variables. The following statements are valid:

proc catmod;
direct X;
model Y=X;
weight wt;
run;
direct;
model Y=X;
run;

The first MODEL statement uses the actual values of X,
and the second MODEL statement uses the four variables
created when PROC CATMOD generates the design matrix. Note
that the preceding statements can be run without a WEIGHT
statement if the input data are raw data rather than cell
counts.

For more details, see the discussions of main and direct
effects in the section "Generation of the Design Matrix".

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.