Frequencies for first 10,000 rows of usetobac variable in nhamcsopd2003 dataset :

       does |
patient use |
   tobacco? |      Freq.     Percent        Cum.
------------+-----------------------------------
      blank |        240        2.40        2.40
        yes |        989        9.89       12.29
         no |      4,669       46.69       58.98
    unknown |      4,102       41.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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