如何使字符变量靠左

data aaa;
input x y$16.@@;
cards;
1 2
2 4
;
run;
data aaa;
length _x $16.;
SET aaa;
_x=put(x,12.);
drop x;
rename _x=x;
run;

如何使x和y一样，前面没有空格。

data aaa;
length _x $16.;
SET aaa;
_x=put(x,12.-l);
drop x;
rename _x=x;
run;

data a;
set aaa;
x=left(x);
run;

data aaa;
input x y$16.@@;
cards;
1 2
2 4
;
run;
data aaa;
length _x $16.;
SET aaa;
_x=left(put(x,12.));
drop x;
rename _x=x;
run;

left()函数：字符左对齐。