运行select语句遇到一个很奇怪的问题，高手帮忙解答一下

shiyiming

data a;
input x @@;
cards;
0 2 3
;
run;

data b1;
set a;
select(x);
when (x=0) y=1;
when (x=2) y=2;
otherwise;
end;
run;

本以为输出的数据集b1第二条观测中y=2，但是结果却是y=缺失值。请高手帮忙解释一下！

shiyiming

[code:3vvarjdj]select(x);
        when (0) y=1;
        when (2) y=2;
end;
/*or*/
select;
        when (x=0) y=1;
        when (x=2) y=2;
end;[/code:3vvarjdj]

shiyiming

谢谢，不过我知道你写的两种方法是正确的，问题是我的程序中，为什么第二行输出的y值是缺失值？因为我的程序日志并没有报错。

shiyiming

to today2009
in your syntax, you are doing like that
condition x= (x=0)?, same as x = 1 because 0 =0.  no, so go to next when
condition x = (x =2)?, same as x = 0 because 0 ^= 2. yes, so get y = 2
....
because for satisfying the condition, your x has to be 0 or 1, so you got the missing value for x = 2 or 3.

shiyiming

是的，多谢！