8.1 Introduction
The Combine data procedure allows the user to concatenate (stack) multiple data sets. The data sets need not contain the same variables. Variables with a shared name will be treated as the same variable in the combined data set. It is important that they have the same value structure. If a variable does not appear in one of the data sets, it is treated as missing data in the combined data set. The user may want to impute the missing values prior to analyzing the combined data set using IMPUTE.
For example, suppose that data set 1 provides variables X and Y, data set 2 provides variables X and Z and data set 3 provides variables Y and Z. COMBINE can be used to concatenate the three data sets and multiply impute the missing values of X, Y and Z to create complete data on all three variables. The multiply imputed combined data sets can then be analyzed using the DESCRIBE, REGRESS or SASMOD modules.
8.2 COMBINE Statements
DATAIN filename;
This keyword identifies the location and name of the data set to be analyzed. See Section 1.4.1 for more information about specifying a filename using the libname statement in SAS or changing the working directory to match the location of the data set. To combine multiple data sets, more than one data set can follow the DATAIN keyword.
DATAOUT filename;
DATAOUT is used to name an output data set produced by the COMBINE procedure.
RUN;
This should be the last statement in the setup file.