Classic DoW loop flagging first variable

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Classic DoW loop flagging first variable

Hi SASCommunity - I have a set of participants and a set of dates that are divided into active(active=1) and postactive(active=0) periods. I'd like to flag the first date of each active period for each partipant. 

For example, in the following dataset I would like to have a FLAG variable as follows (forgive me if syntaxical error here - I'm a NEWBY to SAS):

 

data participantperiods;

input participants dates active FLAG;

datalines;

1  date1  1  1

1  date2  1  0

1  date3  0  0

2  date4  1  1

2  date5  1  0

2  date6  1  0

2  date7  0  0

2  date8  0  0;

run;

 

I would like this to be in the form of a classic 2xDoW loop. This is what I have developed so far, but it is overflagging unfortunately:

 

data WANT;
     do until (last.PARTICIPANT);
          set HAVE;
          by PARTICIPANT;
          if first.PARTICIPANT then FIRSTFLAG=1;
     end;
     do until (last.PARTICIPANT);
          set HAVE;
          by PARTICIPANT;
     output;
     end;

     do until (last.PARTICIPANT);
          set HAVE;
          by PARTICIPANT;
          if FIRSTFLAG=1 and ACTIVE=1 then FIRSTACTIVEFLAG=1;
     end;

     do until (last.case_no);
          set Encountersbydayvendor4;
          by case_no;
          output;
     end;
run;

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‎08-18-2016 03:51 PM
Super User
Posts: 13,562

Re: Classic DoW loop flagging first variable

Posted in reply to dweissner

It appears as if the data is sorted by participants and descending active. If that is the case then this should work:

data want;
   set participantperiods;
   by participants descending active;
   if first.participants and first.active and active=1 then flag=1;
   else flag=0;
run;

if not then sort by participants descending active and date may get what you are looking for.

 

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Solution
‎08-18-2016 03:51 PM
Super User
Posts: 13,562

Re: Classic DoW loop flagging first variable

Posted in reply to dweissner

It appears as if the data is sorted by participants and descending active. If that is the case then this should work:

data want;
   set participantperiods;
   by participants descending active;
   if first.participants and first.active and active=1 then flag=1;
   else flag=0;
run;

if not then sort by participants descending active and date may get what you are looking for.

 

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