Frequencies for first 10,000 rows of usetobac variable in nhamcsopd2004 dataset :

       does |
patient use |
   tobacco? |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        203        2.03        2.03
        yes |      1,192       11.92       13.95
         no |      5,126       51.26       65.21
    unknown |      3,479       34.79      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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