It is not clear. Can you state your problem in a different way?

data mm;
input x y;
cards;
1  5
1  2
1   1
1  3
1 4
1  6
2   3
2   2
2  1
2   6
2   4
;
run;


data nn;
do until(last.x);
set mm;
by x;
retain tmp n 0;
if first.x then do;
num2=0;
n=0;
tmp=y;
end;
else do;
n+1;
tmp+y;
num2=(tmp-y)/n;

end;
output;
end;
run;

掉了sort的一部分程序
data kk;
input x y;
cards;
1  5
1  2
1   1
1  3
1 4
1  6
2   3
2   2
2  1
2   6
2   4
;
run;


proc sort data=kk out=mm;
by x descending y;
run;


data nn;
do until(last.x);
set mm;
by x;
retain tmp n 0;
if first.x then do;
num2=0;
n=0;
tmp=y;
end;
else do;
n+1;
tmp+y;
num2=(tmp-y)/n;

end;
output;
end;
run;

我的理解是这个样子的
1# rwalker

设此表为test(x,y)
proc sql;
     select x,y
     from test as a left join (select x,mean(y) as avg_y from test group by x) as b on a.x=b.x
     where a.y > b.avg_y;
quit;