PROC GLIMMIX: Response Variable Options :: SAS/STAT(R) 9.2 User's Guide, Second Edition

The GLIMMIX Procedure

Response Variable Options

Response variable options determine how the GLIMMIX procedure models probabilities for binary and multinomial data.

You can specify the following options by enclosing them in parentheses after the response variable. See the section Response-Level Ordering and Referencing for more detail and examples.

DESCENDING

DESC

reverses the order of the response categories. If both the DESCENDING and ORDER= options are specified, PROC GLIMMIX orders the response categories according to the ORDER= option and then reverses that order.

EVENT=’category’ $\text{[math]}$ | $\text{[math]}$ keyword

specifies the event category for the binary response model. PROC GLIMMIX models the probability of the event category. The EVENT= option has no effect when there are more than two response categories. You can specify the value (formatted, if a format is applied) of the event category in quotes, or you can specify one of the following keywords:

FIRST: designates the first ordered category as the event. This is the default.
LAST: designates the last ordered category as the event.

ORDER=DATA $\text{[math]}$ | $\text{[math]}$ FORMATTED $\text{[math]}$ | $\text{[math]}$ FREQ $\text{[math]}$ | $\text{[math]}$ INTERNAL

specifies the sort order for the levels of the response variable. When ORDER=FORMATTED (the default) for numeric variables for which you have supplied no explicit format (that is, for which there is no corresponding FORMAT statement in the current PROC GLIMMIX run or in the DATA step that created the data set), the levels are ordered by their internal (numeric) value. If you specify the ORDER= option in the MODEL statement and the ORDER= option in the PROC GLIMMIX statement, the former takes precedence. The following table shows the interpretation of the ORDER= values:

Table 38.7 *continued*
Value of ORDER=	Levels Sorted By
DATA	order of appearance in the input data set
FORMATTED	external formatted value, except for numeric variables with no explicit format, which are sorted by their unformatted (internal) value
FREQ	descending frequency count; levels with the most observations come first in the order
INTERNAL	unformatted value

By default, ORDER=FORMATTED. For the FORMATTED and INTERNAL values, the sort order is machine dependent.

For more information about sort order, see the chapter on the SORT procedure in the Base SAS Procedures Guide and the discussion of BY-group processing in SAS Language Reference: Concepts.

REFERENCE=’category’ $\text{[math]}$ | $\text{[math]}$ keyword

REF=’category’ $\text{[math]}$ | $\text{[math]}$ keyword

specifies the reference category for the generalized logit model and the binary response model. For the generalized logit model, each nonreference category is contrasted with the reference category. For the binary response model, specifying one response category as the reference is the same as specifying the other response category as the event category. You can specify the value (formatted if a format is applied) of the reference category in quotes, or you can specify one of the following keywords:

FIRST: designates the first ordered category as the reference category.
LAST: designates the last ordered category as the reference category. This is the default.

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