如何把每个个体(id)visit>1的x的最大值取出

1. data aaa;
   
2. input id visit x;
   
3. cards;
   
4. 1 1 1
   
5. 1 2 1
   
6. 1 3 3
   
7. 1 4 4
   
8. 2 1 1
   
9. 2 2 3
   
10. 3 1 2
    
11. 3 2 2
    
12. 3 3 3
    
13. ;
    
14. run;

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如何把每个个体(id)visit>1的x的最大值取出，放在visit=1的后面，结果如下：
id visit x fl
1 1 1 4
1 2 1 .
1 3 3 .
1 4 4 .
2 1 1 3
2 2 3 .
3 1 2 3
3 2 2 .
3 3 3 .



如能用data步实现最后，谢谢！

data bbb;set aaa;run;
proc sort data=bbb;by id visit;
run;
data c;set bbb;by id ;
if last.id;
run;
data c;set c;
if visit=1 then delete;
run;
data c;set c;
visitpass=1;
run;/*选出visit>1的个体,用visitpass标记*/
proc sort data=bbb;by id x;
run;
data d;set bbb;by id x;
if last.id;
run;
data d;set d;fl=x;run;/*选出x最大的个体*/
data cd;merge c d;by id;
run;
data cd;set cd;
if visitpass=. then delete;
run;
data cdd;set cd;keep id fl;run;
data eee;set bbb;by id ;
if first.id;
run;
data ccc;merge eee cdd;by id ;
run;
data ddd;merge ccc aaa;by id visit;run;

proc sort data=aaa(where=(visit>1)) out=bbb;by id visit x;run;
data bbb;
set bbb;
by id visit x;
if last.id;
visit=1;
rename x=fl;
run;
proc sort data=aaa;by id visit;run;
data result;
merge aaa(in=a) bbb(in=b);
by id visit;
if a;
run;

1. proc sql;
   
2.         create table bb as
   
3.         select distinct id, 1 as visit, max(x) as max_x
   
4.         from aaa
   
5.         where visit>1
   
6.         group by 1
   
7.         order by 1,2
   
8.         ;
   
9. quit;
   
10.        
    
11. proc sort data=aaa;
    
12.         by id visit;
    
13. run;
    
14. 
    
15. data aaa_;
    
16.         merge aaa(in=a) bb;
    
17.         by id visit;
    
18.         if a;
    
19. run;

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