SAS Creating a count variable that resets - sas

Question

I'd like to create a count variable that resets every 6 months by the manner of crime. Here is my code :
proc sort data=incident_v1;
by incident year;
run;
Data incident_v2;
set incident_v1 end= eof;
by incident;
do i=1 until (eof);
do j = 1 to 6;
retain ID 0;
if first.incident then ID=ID +1;
end;
end;
run;
Year-mo incident # of incidents Count every six months
199901 car-jack 6 1
199902 car-jack 7 2
199903 car-jack 12 3
199904 car-jack 8 4
199905 car-jack 13 5
199906 car-jack 8 6
199907 car-jack 13 1
199908 car-jack 6 2
199909 car-jack 8 6
200001 robbery 5 1
200002 robbery 5 2
200003 robbery 8 3
200004 robbery 4 4
200005 robbery 6 5
200006 robbery 14 6

Answer 1

Try this:
proc sort data=incident_v1;
by incident year;
run;
Data incident_v2;
set incident_v1 end= eof;
by incident;
/*Reset Count if New Incident Type*/
if first.incident then Incident_count_6_mnths = 0;
/*Reset Count if month is 07 (which from your data below I believe to be actually year & month and of the form YYYYMM*/
if substr(year,5,2) = "07" then Incident_count_6_mnths = 0;
/*if year is a not a text field you will have to use: substr(compress(put(year,8.)),5,2) = "07" */
/*Add a counter - please note there is no need for a retain statement as the +1 will automatically retain.*/
Incident_count_6_mnths+1;
run;