Selecting Variables (1)

Merging SAS Data Sets

Selecting Variables

In addition to selecting observations, you can select variables to appear in your output data set. You name the variables you want to drop or keep using the DROP= and KEEP= data set options. You can use the KEEP= option instead of the DROP= option if more variables are dropped than kept.

General form, DROP= and KEEP= data set options:
(DROP=variable(s))
(KEEP=variable(s))

where

the DROP= or KEEP= option, in parentheses, follows the name of the data set containing the variables to be dropped or kept
variable(s) is the name of one or more variables, separated by blanks.

For example, the DATA step below reads all variables from Clinic.Demog and all variables except Weight from Clinic.Visit, and then excludes the variable ID from Clinic.Combined after the merge processing is complete.

     data clinic.combined(drop=id);
        merge clinic.demog(in=InDemog 
                           rename=(date=BirthDate)) 
              clinic.visit(drop=weight in=InVisit);  
        by id;
        if indemog and invisit;
     run;
     proc print data=clinic.combined;
     run;

Obs Age Sex BirthDate Visit SysBP DiasBP VisitDate

1 21 m 05/22/75 1 140 85 11/05/98

2 21 m 05/22/75 2 138 90 10/13/98

3 21 m 05/22/75 3 145 95 07/04/98

4 32 m 06/15/63 1 121 75 04/14/98

5 24 f 08/17/72 1 118 68 08/12/98

6 24 f 08/17/72 2 112 65 08/21/98

7 . 03/27/69 1 143 86 03/30/98

8 44 f 02/24/52 1 132 76 02/27/98

9 44 f 02/24/52 2 132 78 07/11/98

10 44 f 02/24/52 3 134 78 04/16/98

Obs	Age	Sex	BirthDate	Visit	SysBP	DiasBP	VisitDate
1	21	m	05/22/75	1	140	85	11/05/98
2	21	m	05/22/75	2	138	90	10/13/98
3	21	m	05/22/75	3	145	95	07/04/98
4	32	m	06/15/63	1	121	75	04/14/98
5	24	f	08/17/72	1	118	68	08/12/98
6	24	f	08/17/72	2	112	65	08/21/98
7	.		03/27/69	1	143	86	03/30/98
8	44	f	02/24/52	1	132	76	02/27/98
9	44	f	02/24/52	2	132	78	07/11/98
10	44	f	02/24/52	3	134	78	04/16/98