用笛卡尔积就行，只不过数据量不能很大了

proc sql noprint;
        create table result as
                select a.x,a.y,b.x as x1,b.y as y1
                from a as a,a as b
                where a.x = b.x and a.y < b.y;
quit;

proc sql noprint;
        create table result1 as
                select distinct x,SUM(LOG(y1)/LOG(y)) as logsum
                from result
                group by x;
quit;

楼主貌似将SUM(LOG(y1/y))敲成SUM(LOG(y1)/LOG(y))了