Frequencies for first 10,000 rows of alcdrug variable in nhamcsed1995 dataset :

   is visit |
 alcohol or |
       drug |
   related? |      Freq.     Percent        Cum.
------------+-----------------------------------
    Neither |      7,089       70.89       70.89
    Alcohol |        270        2.70       73.59
       Drug |        188        1.88       75.47
       Both |         71        0.71       76.18
    Unknown |      2,382       23.82      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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