Anyone can explain why x3=0? I thought x3 returns the number of missing values of {1, 0, ., 2, 5, ., 1, 0} (combine numbers for x1 and numbers for x2), so x3 should be 2, but it's 0. I get confused this.
data one;
x1=nmiss(1, 0, ., 2, 5, .);
x2=nmiss(1, 0);
x3=nmiss(of x1-x2);
put x1= x2= x3=;
run;