Frequencies for first 10,000 rows of contsub4 variable in nhamcsopd2007 dataset :

       for rx4, controlled |
     substance status code |      Freq.     Percent        Cum.
---------------------------+-----------------------------------
schedule i (research only) |          1        0.01        0.01
               schedule ii |         45        0.45        0.46
              schedule iii |         28        0.28        0.74
               schedule iv |         95        0.95        1.69
                schedule v |         12        0.12        1.81
                no control |      2,280       22.80       24.61
              undetermined |         26        0.26       24.87
                         . |      7,513       75.13      100.00
---------------------------+-----------------------------------
                     Total |     10,000      100.00

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