Frequencies for first 10,000 rows of usetobac variable in namcs2002 dataset :

       Does |
patient use |
   tobacco? |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        414        4.14        4.14
        Yes |        939        9.39       13.53
         No |      6,220       62.20       75.73
    Unknown |      2,427       24.27      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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