OBS Counts Within Group

[mdavidson]

Hi -- I'm in need of a way to flag observations in a dataset within a group by groups of 5. Is there an easy way to do this?

For example: 

GROUP	OBS	WANT
1	1	1
1	2	1
1	3	1
1	4	1
1	5	1
1	6	2
1	7	2
1	8	2
1	9	2
1	10	2
1	11	3
1	12	3
2	1	1
2	2	1
2	3	1
2	4	1
2	5	1
2	6	2
2	7	2
2	8	2
2	9	2
2	10	2

[Reeza]

Try the MOD() function along with BY processing to reset COUNT at the start of each GROUP. .

IF mod(obs, 5) = 1 then count+1;

[novinosrin]

demo

data have;
input GROUP	OBS	;
cards;
1	1	1
1	2	1
1	3	1
1	4	1
1	5	1
1	6	2
1	7	2
1	8	2
1	9	2
1	10	2
1	11	3
1	12	3
2	1	1
2	2	1
2	3	1
2	4	1
2	5	1
2	6	2
2	7	2
2	8	2
2	9	2
2	10	2
;
data want;
set have;
by group;
if first.group then want=1;
if mod(obs,5)=0 then do; output;want+1;end;
else output;
run;

[mdavidson]

I think that's close but not the expected result. For example, check the first 3 rows of the Audi group:

data a;
set sashelp.cars;
by make;
obs=_n_;
if first.make then want=1;
if mod(obs,5)=0 then do; output;want+1;end;
else output;
keep obs make model want;
run;

[novinosrin · Accepted solution]

data a;
do _n_=1 by 1 until(last.make);
set sashelp.cars;
by make;
if first.make then want=1;
if mod(_n_,5)=0 then do; output;want+1;end;
else output;
end;
keep  make model want;
run;

[mdavidson]

Thank you, this is perfect! Genius!

[novinosrin]

@mdavidson You are welcome. My apologies for the lack of attention to detail earlier.  I have had this problem for ages 😞 . Have a good day