Frequencies for first 10,000 rows of contsub6 variable in nhamcsed1995 dataset :

 controlled |
  substance |
   code for |
    drug #6 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |          5        0.05        0.05
          3 |          6        0.06        0.11
          4 |          7        0.07        0.18
          5 |          1        0.01        0.19
          6 |        162        1.62        1.81
          7 |          6        0.06        1.87
          . |      9,813       98.13      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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