Frequencies for first 10,000 rows of contsub7 variable in nhamcsed2006 dataset :

       for rx7, controlled |
     substance status code |      Freq.     Percent        Cum.
---------------------------+-----------------------------------
               schedule ii |          8        0.08        0.08
              schedule iii |          6        0.06        0.14
               schedule iv |          5        0.05        0.19
                no control |         96        0.96        1.15
                         . |      9,885       98.85      100.00
---------------------------+-----------------------------------
                     Total |     10,000      100.00

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