Frequencies for first 10,000 rows of smokcig variable in nhamcsopd1995 dataset :

       does |
    patient |
      smoke |
cigarettes? |      Freq.     Percent        Cum.
------------+-----------------------------------
        Yes |      1,181       11.81       11.81
         No |      4,236       42.36       54.17
    Unknown |      4,583       45.83      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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