How can I get the identification number with each groups? - sas

Question

The following is a brief of my data sheet,
stnd_y person_id recu_day date
2002 100 20020929 02-09-29
2002 100 20020930 02-09-30
2002 100 20021002 02-10-02
2002 101 20020927 02-09-27
2002 101 20020928 02-09-28
2002 102 20021001 02-10-01
2002 103 20021003 02-10-03
2002 104 20021108 02-11-08
2002 104 20021112 02-11-12
And, I want to make those as follows
stnd_y person_id recu_day date Admission
2002 100 20020929 02-09-29 1
2002 100 20020930 02-09-30 2
2002 100 20021002 02-10-02 3
2002 101 20020927 02-09-27 1
2002 101 20020928 02-09-28 2
2002 102 20021001 02-10-01 1
2002 103 20021003 02-10-03 1
2002 104 20021108 02-11-08 1
2002 104 20021112 02-11-12 2
I mean, I want to make a variable for admission frequency personally with recu_day and date (this variables mean the date of hospitalization).
And then, I used the following with sas,
proc sort data=old out=new;
by person_id recu_day;
data new1;
set new;
retain admission 0;
by person_id recu_day;
if recu_day^=lag(recu_day) and(or) person_id^=lag(person_id) then
admission+1;
run;
And also,
data new1;
set new ;
by person_id recu_day;
retain adm 0;
if first.person_id and(or) first.recu_day then admission=admission+1;
run;
But, those are not working.
How can I solve this? Please let me know about this.

Answer 1

You're pretty close with the 2nd attempt, but your main problem is that you don't reset admission each time person_id changes.
It's also not necessary to use first.recu_day as this is 1 for every record in your sample data. first.person_id is sufficient as you want to increment the number by 1 if the peson_id hasn't changed from the previous row.
Including recu_day in the by statement is useful however, as this will force an error if the data isn't sorted properly.
data have;
input stnd_y person_id recu_day date :yymmdd8.;
format date yymmdd8.;
datalines;
2002 100 20020929 02-09-29
2002 100 20020930 02-09-30
2002 100 20021002 02-10-02
2002 101 20020927 02-09-27
2002 101 20020928 02-09-28
2002 102 20021001 02-10-01
2002 103 20021003 02-10-03
2002 104 20021108 02-11-08
2002 104 20021112 02-11-12
;
run;
data want;
set have;
by person_id recu_day;
if first.person_id then admission=0;
admission+1;
run;