Renaming Variables (1)

Merging SAS Data Sets

Renaming Variables

Sometimes you may have variables with the same name in more than one input data set. In this case, DATA step match-merging overwrites values of the like-named variable in the first data set in which it appears with values of the like-named variable in subsequent data sets.

For example, Clinic.Demog contains the variable Date (date of birth), and Clinic.Visit also contains Date (date of clinic visit in 1998). The DATA step below overwrites the date of birth with the date of clinic visit.

     data clinic.combined;       
        merge clinic.demog clinic.visit; 
        by id;
     run;
     proc print data=clinic.combined;
     run;

The following output shows the effects of overwriting variable values in the Clinic.Combined data set. In most observations, the date is now the date of the clinic visit. In observation 11, the date is still the birth date because the value for the date of the clinic visit is missing.

Obs ID Age Sex Date Visit SysBP DiasBP Weight

1 A001 21 m 11/05/98 1 140 85 195

2 A001 21 m 10/13/98 2 138 90 198

3 A001 21 m 07/04/98 3 145 95 200

4 A002 32 m 04/14/98 1 121 75 168

5 A003 24 f 08/12/98 1 118 68 125

6 A003 24 f 08/21/98 2 112 65 123

7 A004 . 03/30/98 1 143 86 204

8 A005 44 f 02/27/98 1 132 76 174

9 A005 44 f 07/11/98 2 132 78 175

10 A005 44 f 04/16/98 3 134 78 176

11 A007 39 m 11/11/57 . . .

12 A008 . 05/22/98 1 126 80 182

Obs	ID	Age	Sex	Date	Visit	SysBP	DiasBP	Weight
1	A001	21	m	11/05/98	1	140	85	195
2	A001	21	m	10/13/98	2	138	90	198
3	A001	21	m	07/04/98	3	145	95	200
4	A002	32	m	04/14/98	1	121	75	168
5	A003	24	f	08/12/98	1	118	68	125
6	A003	24	f	08/21/98	2	112	65	123
7	A004	.		03/30/98	1	143	86	204
8	A005	44	f	02/27/98	1	132	76	174
9	A005	44	f	07/11/98	2	132	78	175
10	A005	44	f	04/16/98	3	134	78	176
11	A007	39	m	11/11/57		.	.	.
12	A008	.		05/22/98	1	126	80	182