如何剔除只有一种取值的变量

要求如题：如何剔除只有一种取值的变量
举一个例子，有一个数据集，包含a, b, c三个字符型变量，其中，b这个变量的取值只有一种，需要删掉，怎么用SAS表达出这种过程？


data a ;
input a$ b$ c$;
cards;
Jeremy M 1960
James M 1963
Richard M 1969
;
run;

data allvar;
set sashelp.vcolumn;
where libname="WORK" and memname="A";
keep name;
run;

data _null_;
set allvar;
call execute('proc sql;
               create table varnobs'||cats(_n_)||' as
               select '||quote(strip(name))||' as varname, count(distinct '||strip(name)||') as nobs
               from a;
               quit;');
run;

data nobs;
set varnobs:;
run;

proc sql noprint;
select varname into: dropvar separated by " "
from nobs
where nobs=1;
quit;

data wanted;
set a;
drop &dropvar;
run;

input之后被吞了两个dollar符号

wwang111 发表于 2017-11-24 14:25
data allvar;
set sashelp.vcolumn;
where libname="WORK" and memname="A";

感谢大神！！！

1. data a ;
   
2. input a$ b$ c;
   
3. cards;
   
4. Jeremy M 1960
   
5. James M 1960
   
6. Richard M 1960
   
7. ;
   
8. run;
   
9. 
   
10. data allvar;
    
11. set sashelp.vcolumn;
    
12. where libname="WORK" and memname="A";
    
13. keep name;
    
14. run;
    
15. 
    
16. proc sql noprint;
    
17. select count(distinct name) into:  d from allvar;
    
18. select name into:  m1 - : m%sysfunc(strip(&d.))  from allvar;
    
19.    quit;
    
20. 
    
21. %macro jj;
    
22. %do i=1 %to &d.;
    
23. proc sql noprint;
    
24. select count(distinct &&m&i) into:  n&i from a;
    
25.           quit;
    
26. data a;
    
27. set a;
    
28. %if &&n&i.=1 %then %do;drop &&m&i.;%end;
    
29. %end;
    
30. run;
    
31. %mend;
    
32. %jj;

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