- data a;
- x=1;
- output;
- x=2;
- output;
- run;
- data b;
- x=3;
- output;
- x=4;
- output;
- run;
- data _null_;
- put 'START ' ina inb x;
- set a(in=ina) b(in=inb);
- put 'END ' ina inb x;
- run;
START 0 0 .
END 1 0 1
START 1 0 1
END 1 0 2
START 1 0 2
END 0 1 3
START 0 1 3
END 0 1 4
START 0 1 4
自动retain set进来的变量对于line by line的data步来说,多了一个利器,相当于自动多了一个lag1的PDV
很多时候让lag函数变得不那么必须