Frequencies for first 10,000 rows of alcdrug variable in nhamcsed1993 dataset :

       is visit |
alcohol or drug |
       related? |      Freq.     Percent        Cum.
----------------+-----------------------------------
        Neither |      8,543       85.43       85.43
Alcohol related |        270        2.70       88.13
   Drug related |        192        1.92       90.05
           Both |         54        0.54       90.59
        Unknown |        941        9.41      100.00
----------------+-----------------------------------
          Total |     10,000      100.00

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