How Do I create a ID based on a prior observation?

[southbaymax]

If I had these values in excel

BR     VALUE

1        7184
0        9759
1        9988

0        6780

0        6398

1        7107

0        5776

0        3719

and I used this formula in excel IF(A2=1,B2,B1)

I would get this.

BR     VALUE    ID

1        7184       
0        9759       7184
1        9988       9988

0        6780       9988

0        6398       9988

1        7107       7107

0        5776       7107

0        3719       7107

How can I do the same thing in SAS?

[Astounding · Accepted solution]

It's a little convoluted because of the need to keep the first ID blank.  If I understand it correctly:

data want;

set have;

if BR=1 then latest_value = value;

retain latest_value;

if _n_ > 1 then value = latest_value;

drop latest_value;

run;

That should work for the data you posted.  I'm just not 100% certain of the requirements for some of the possibilities such as what happens if BR=0 for the first observation.

[Criptic]

Just to elaborate a bit on the code posted by @Astounding and formatting it:

data work.table_1;
	input br value;
	datalines;
1        7184
0        9759
1        9988
0        6780
0        6398
1        7107
0        5776
0        3719
;
run;

* _id is a temp variable which stores the latest value where br is 1;
data work.table_2(drop=_id);
	length id 8.;
	set work.table_1;
	
	if br=1 then
		_id = value;

	* _N_ contains the current iteration number;
	if _N_ > 1 then
		id = _id;

	* retains the value from iteration to iteration;
	retain _id;
run;