Frequencies for first 10,000 rows of contsub3 variable in nhamcsopd1998 dataset :

 controlled |
  substance |
   code for |
 medication |
         #3 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         25        0.25        0.25
          3 |         12        0.12        0.37
          4 |         64        0.64        1.01
          5 |          1        0.01        1.02
          6 |      1,874       18.74       19.76
          7 |         53        0.53       20.29
          . |      7,971       79.71      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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