The FMM Procedure

Response Variable Options

Response variable options determine how the FMM procedure models probabilities for binary data.

You can specify the following response-options by enclosing them in parentheses after the response variable. The default is ORDER=FORMATTED.

DESCENDING DESC

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

EVENT=’category’ | keyword

specifies the event category for the binary response model. PROC FMM models the probability of the event category. 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=order-type

specifies the sort order for the levels of the response variable. You can specify the following values for order-type:

DATA: sorts the levels by order of appearance in the input data set.
FORMATTED: sorts the levels by external formatted value, except for numeric variables with no explicit format, which are sorted by their unformatted (internal) value.
FREQ: sorts the levels by descending frequency count; levels with the most observations come first in the order.
INTERNAL: sorts the levels by unformatted value.
FREQDATA: sorts the levels by order of descending frequency count, and within counts by order of appearance in the input data set when counts are tied.
FREQFORMATTED: sorts the levels by order of descending frequency count, and within counts by formatted value (as above) when counts are tied.
FREQINTERNAL: sorts the levels by order of descending frequency count, and within counts by unformatted value when counts are tied.

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 FMM 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 FMM statement, the former takes precedence.

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’ | keyword REF=’category’ | keyword

specifies the reference category for categorical models. For the binary response model, specifying one response category as the reference category 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 quotation marks, 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.

The reference category in multinomial, Dirichlet-multinomial, and multinomial cluster models is determined by the order in which you specify the response variables.