data a;
input id y z;
cards;
1 2 3
2 2 3
3 2 3
4 2 3
;
run;
data b;
input id y z x;
cards;
1 2 3 4
2 2 3 4
3 2 . 4
4 2 3 4
5 . 3 4
6 2 . 4
7 . 3 4
;
run;
data c;
merge a b;
retain yy zz;
if y ne . then yy=y;
if z ne . then zz=z;
y=yy;z=zz;
keep id y z x;
by id;
run;