Frequencies for first 10,000 rows of alcdrug variable in nhamcsed1992 dataset :

       Is visit |
alcohol or drug |
       related? |      Freq.     Percent        Cum.
----------------+-----------------------------------
        Neither |      9,556       95.56       95.56
Alcohol related |        266        2.66       98.22
   Drug related |        138        1.38       99.60
           Both |         40        0.40      100.00
----------------+-----------------------------------
          Total |     10,000      100.00

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