Excluding Unmatched Observations (2)

Merging SAS Data Sets

Excluding Unmatched Observations

Creating Temporary IN= Variables

For example, suppose you want to match-merge the data sets Clinic.Demog and Clinic.Visit and select only observations that appear in both data sets.

First, you use IN= to create two temporary variables, InDemog and InVisit. The IN= variable is a temporary variable that is available to program statements during the DATA step, but it is not included in the SAS data set that is being created.

General form, IN= data set option:

(IN=variable)

where

the IN= option, in parentheses, follows the data set name
variable names the variable to be created.

Within the DATA step, the value of the variable is 1 if the data set contributed data to the current observation, and 0 otherwise.

The DATA step containing the IN= options appears below. The first IN= creates the temporary variable InDemog, which is set to 1 when an observation from Clinic.Demog contributes to the current observation; otherwise, it is set to 0. Likewise, the value of InVisit depends on whether Clinic.Visit contributes to an observation or not.

data clinic.combined; merge clinic.demog(in=indemog) clinic.visit(in=invisit rename=(date=BirthDate)); by id; run;

When you specify multiple data set options for a given data set, enclose them in a single set of parentheses.