Frequencies for first 10,000 rows of smokcig variable in namcs1994 dataset :

       does |
    patient |
      smoke |
cigarettes? |      Freq.     Percent        Cum.
------------+-----------------------------------
        Yes |      1,209       12.09       12.09
         No |      6,369       63.69       75.78
    Unknown |      2,087       20.87       96.65
      Blank |        335        3.35      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016