Frequencies for first 10,000 rows of usetobac variable in nhamcsopd2006 dataset :

    tobacco |
   use: not |
   current, |
    current |      Freq.     Percent        Cum.
------------+-----------------------------------
      Blank |        325        3.25        3.25
Not current |      5,060       50.60       53.85
    Current |      1,254       12.54       66.39
    Unknown |      3,361       33.61      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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