When match-merging,
specify these options in either the DATA statement or the MERGE statement,
depending on whether you want to reference the variables in that DATA
step:
-
To reference a variable in the
original data set (in a subsetting IF statement, for example) specify
the variable in the DROP= option in the DATA statement. Otherwise,
you might get unexpected results and your variable would be uninitialized.
data clinic.merged (drop=id);
-
To not reference certain variables
and exclude them from the new data set, specify them in the DROP=
option in the MERGE statement.
merge clinic.demog(in=indemog
rename=(date=BirthDate))
clinic.visit(drop=weight in=invisit
rename=(date=VisitDate));
When used in the DATA
statement, the DROP= option simply drops the variables from the new
data set. However, the variables are still read from the original
data set and are available for processing within the DATA step.