Frequencies for first 10,000 rows of smokcig variable in namcs1993 dataset :

       does |
    patient |
      smoke |
cigarettes? |      Freq.     Percent        Cum.
------------+-----------------------------------
        Yes |      1,032       10.32       10.32
         No |      6,883       68.83       79.15
    Unknown |      1,708       17.08       96.23
      Blank |        377        3.77      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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