Frequencies for first 10,000 rows of alcdrug variable in nhamcsed1994 dataset :

       is visit |
alcohol or drug |
       related? |      Freq.     Percent        Cum.
----------------+-----------------------------------
        Neither |      8,247       82.47       82.47
Alcohol related |        245        2.45       84.92
   Drug related |        170        1.70       86.62
           Both |         42        0.42       87.04
        Unknown |      1,296       12.96      100.00
----------------+-----------------------------------
          Total |     10,000      100.00

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