if data for any row missing then delete whole group

[Takdir]

data work.delete;
input firm $ year profit;
datalines;
A 2001 90
A 2002 80
A 2003 70
A 2004 90
A 2005 60
B 2001 70
B 2002 80
B 2003 90
C 2001 70
C 2002 80
C 2003 90
C 2004 60
C 2005 80
D 2001 10
D 2002 20

I wish to delete those firms that does not have observation for 5 years. My desired output is
A 2001 90
A 2002 80
A 2003 70
A 2004 90
A 2005 60
C 2001 70
C 2002 80
C 2003 90
C 2004 60
C 2005 80

[Astounding]

This approach assumes your data is sorted by FIRM:

data want;

counter=0;

do until (last.firm);

   set have;

   by firm;

   counter + 1;

end;

do until (last.firm);

   set have;

   by firm;

   if counter >= 5 then output;

end;

drop counter;

run;

The top loop counts observations, and the bottom reads the same observations and outputs appropriately.

[novinosrin · Accepted solution]

data work.delete;
input firm $ year profit;
datalines;
A 2001 90
A 2002 80
A 2003 70
A 2004 90
A 2005 60
B 2001 70
B 2002 80
B 2003 90
C 2001 70
C 2002 80
C 2003 90
C 2004 60
C 2005 80
D 2001 10
D 2002 20
;

proc sql;
create table want as
select *
from delete
group by firm
having count(distinct year)>=5;
quit;

[novinosrin]

data work.delete;
input firm $ year profit;
datalines;
A 2001 90
A 2002 80
A 2003 70
A 2004 90
A 2005 60
B 2001 70
B 2002 80
B 2003 90
C 2001 70
C 2002 80
C 2003 90
C 2004 60
C 2005 80
D 2001 10
D 2002 20
;
data _null_;
if _n_=1 then do;
   dcl hash H (dataset:'delete',ordered: "A", multidata:'y') ;
   h.definekey  ("firm") ;
   h.definedata (all:'y') ;
   h.definedone () ;
end;
  _n_=0;
do until(last.firm);
set delete end=lr;
by firm year;
if first.year then _n_+1;
end;
if _n_<5 then h.remove();
if lr then h.output(dataset:'want');
run;