Changes and Enhancements to SAS/STAT Software in V7 and V8

GENMOD Procedure

The earlier version of PROC GENMOD used a prototype Output Delivery System. This system has been totally rewritten; as a consequence, some of the syntax associated with ODS has changed. In particular, the ODS statement now replaces the use of the MAKE statement and _PRINT_ and _DISK_ global variables. The MAKE statement continues to be supported (except for its NOPRINT option), but the ODS statement provides much greater functionality and you should convert to using it. In addition, several of the table names and associated variable names in the GENMOD procedure have changed; see the chapter on the GENMOD procedure for complete information. The OUTPUT and the TEMPLATE procedures have changed. See Chapter 15, "Using the Output Delivery System," in this book for more information about the Output Delivery System.

PROC GENMOD now includes an LSMEANS statement that provides an extension of least squares means to the generalized linear model. In addition, the ESTIMATE statement is now supported. The new DIST=NEGBIN option in the MODEL statement specifies the negative binomial distribution, and the DIST=MULT option specifies the multinomial distribution. The log function is the default link for the negative binomial distribution, and the cumulative logit is the default link function for the multinomial distribution. Note that only the ordinal model is supported for the multinomial distribution, including the links CLOGIT for cumulative logit, CPROBIT for cumulative probit, and CCLL for cumulative complementary log-log.

The GEE facilities have also been updated. Type 3 tests are now provided for model effects, and the CONTRAST statement can be used for the GEE parameter estimates. The LSMEANS and ESTIMATE statements also apply to GEE parameter estimation. The method of alternating logistic regressions (ALR) is available with the LOGOR option in the REPEATED statement, which specifies the regression structure of the log odds ratio used to model the association of the responses from subjects for binary data. You can also fit the GEE model to ordinal data now, using the independent working correlation structure.

The NAMELEN= option in the PROC GENMOD statement enables you to specify the length of effect names to be between 20 and 200 characters.

The DESCENDING option in the PROC statement specifies that the levels of the response variable be sorted in reverse order. The RORDER= option defines the ordering of the levels of the response variable. The procedure now includes an ID option in the MODEL statement for the OBSTATS table, and new variables have been added to the OUTPUT= data set.

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