用retain来试试

data b;
set raw;
by subjid;
retain a ;
if first.subjid then a=.;
if value2^=. then a=value2;
run;

Thanks!
3# honghejing

data raw;
input subjid $ visit value1 value2;
retain v;
if first.value2 then v=value2;else
if value2=. then value2=v;else
v=value2;
drop v;
cards;
001 1 100 110
001 2 101 111
001 3 102 112
001 4 103 .
002 1 100 110
002 2 101 111
002 3 102 .
003 1 100 110
003 2 101 111
003 3 102 112
003 4 103 113
run;

Thank you!
5# zane_gao