The SURVEYLOGISTIC Procedure

Response Variable Options

You specify the following options by enclosing them in parentheses after the response variable:

DESCENDING DESC

reverses the order of response categories. If both the DESCENDING and the ORDER= options are specified, PROC SURVEYLOGISTIC orders the response categories according to the ORDER= option and then reverses that order. See the section Response Level Ordering for more detail.

EVENT=’category’ | keyword

specifies the event category for the binary response model. PROC SURVEYLOGISTIC 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. The default is EVENT=FIRST.

FIRST: designates the first ordered category as the event
LAST: designates the last ordered category as the event

One of the most common sets of response levels is {0,1}, with 1 representing the event for which the probability is to be modeled. Consider the example where Y takes the values 1 and 0 for event and nonevent, respectively, and Exposure is the explanatory variable. To specify the value 1 as the event category, use the following MODEL statement:

   model Y(event='1') = Exposure;

ORDER=DATA | FORMATTED | FREQ | INTERNAL

specifies the sort order for the levels of the response variable. By default, ORDER=INTERNAL. For ORDER=FORMATTED and ORDER=INTERNAL, the sort order is machine-dependent.

When the default ORDER=FORMATTED is in effect for numeric variables for which you have supplied no explicit format,

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

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’ | keyword REF=’category’ | 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. The default is REF=LAST.

FIRST: designates the first ordered category as the reference
LAST: designates the last ordered category as the reference