有条件保留

data test;
input x y;
cards;
1 .
2 .
3 4
4 .
5 1
6 4
7 3
;
run;


   请问如何才能保存两个x=4的那个观测   因为 被指向了两次。  而且两个3的观测  因为一次是因为有数值 一次是被指向了

这样能解决你的问题吗？

proc sql;
create table step1 as
select * from test
where y ne . or x in (select y from test where y ne .);
quit;

data fmt;
set step1;
retain fmtname "point";
rename x=start y=label;
run;

proc format cntlin=fmt;
run;

data step2;
set step1(keep=y);
where y ne .;
x=input(put(y,point.),best.);
rename y=x x=y;
run;

proc sort data=step2;
by x y;
run;

data step3;
set step2;
by x y;
if first.x=1 and last.x=1 and y=. then delete;
if first.x and y=. then delete;
run;

data wanted;
set step1 step3;
run;

proc sort data=wanted;
by x;
run;