proc sql;
create table tmp as
select a.stkcd,
case
  when b.cnt<5 or (b.cnt>=5 and b.cnt=c.cnt) then year
  else a.ygs
end as ygs
from gsvot5 as a left join
  (select stkcd, count(*) as cnt from gsvot5 group by stkcd) as b
on a.stkcd=b.stkcd
left join
  (select stkcd, count(*) as cnt from gsvot5(where=(ygs=0)) group by stkcd) as c
on a.stkcd=c.stkcd;
quit;

proc sql;
create table tmp as
select a.stkcd,
case
  when b.cnt<5 or (b.cnt>=5 and a.ygs=0) then year
  else a.ygs
end as ygs
from gsvot5 as a left join
  (select stkcd, count(*) as cnt from gsvot5 group by stkcd) as b
on a.stkcd=b.stkcd;
quit;

xuexi xuexi xuexi

对于每个stkcd , 如果ygs的观测小于5个，那么则把year赋值给ygs。如果ygs观测大于等于5，如果它的值是都是0，那么仍然把year赋值给ygs.否则，那么则保持不变