Extract Week from first.date

[AZIQ1]

Hi,

data have;

input id date ;

datalines;                     

id   date

1  01/01/2016

1  01/14/2016

1  01/22/2016

2 02/03/2016

2 04/03/2016

run;

I want to extract week from the first date for the id (observation) and add the same value to others even if the others are different eg

Data want

id  data                week

1  01/01/2016         1

1  01/14/2016         1

1  01/22/2016         1

2 02/08/2016          2

2 04/25/2016          2

Thank you

[mohamed_zaki · Accepted solution]

data have;
input id date mmddyy10. ;
cards;                     
1 01/01/2016
1 01/14/2016
1 01/22/2016
2 02/16/2016
2 04/03/2016
;
run;
 proc sort  data=have;
 by id date;
 run;
 
 
 data want ;
 set have;
 by id;
 retain week;
 if first.id then  week=intck('week',intnx('month',date,0),date)+1; 
 run;