Frequencies for first 10,000 rows of alcdrug variable in nhamcsed1996 dataset :

   is visit |
 alcohol or |
       drug |
   related? |      Freq.     Percent        Cum.
------------+-----------------------------------
    Neither |      7,016       70.16       70.16
    Alcohol |        307        3.07       73.23
       Drug |        185        1.85       75.08
       Both |         54        0.54       75.62
    Unknown |      2,438       24.38      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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