data a; input x1 x2 y $; sumx=sum(of x1-x2); datalines; 1 3.4 A 2 4.6 B 5 -3.2 B ; run; data a; set a; if y="a" then z=x2-x1; else z=x2; run; proc contents data=a position; run; proc print data=a; var x1--z; run;