Handbook of SAS DATA Step Programming

55BY-Group Processing in the DATA Step

else output sas4_1_d;

run;

title 'Non-duplicated records';

proc print data = sas4_1_s;

run;

title 'Duplicated records';

proc print data = sas4_1_d;

run;

Output from Program 4.3:

Non-duplicated records

Obs ID SCORE

1 A01 2

2 A02 2

3 A02 4

Duplicated records

Obs ID SCORE

1 A01 3

2 A01 3

4.2.3 Obtaining the Most Recent Non-Missing

Data within Each BY Group

Longitudinal data, such as patients with repeated measurements over

time, are often encountered in the clinical eld. For example, a patient

mayhavemultiple measurements of weight, blood pressure, total cholesterol,

or blood glucose level over several medical visits, but may not have all these

values recorded every time. Researchers ma