mv = {.};

dataloop freqdata dumy;
    extern mv;
    code cage with
        1  for  age >= 6,
        0  for age < 6,
        mv for age $== mv;

    recode  sex with
       1  for sex $== "M",
       0  for sex $== "F",
       mv for sex $== mv;
    keep cage sex pay age;
endata;