data test;
input id$2. start end drug ;
attrib start format =date9. informat=date9.;
attrib end format =date9. informat=date9.;
datalines;
1 01JAN2015 14FEB2015 0
1 18FEB2015 30APR2015 1
2 01jan2015 28JAN2015 1
2 01apr2015 30apr2015 1
3 01JAN2015 14FEB2015 1
3 01JAN2015 14FEB2015 0
;
run; I have the following data. I want to flag the first date, keep the id, drug. If the id have both drug 0 and drug 1 on the same date then delete. Output data 1 01JAN2015 14FEB2015 0
2 01jan2015 28JAN2015 1
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