Frequencies for first 10,000 rows of contsub6 variable in namcs1999 dataset :

 controlled |
  substance |
   code for |
 medication |
         #6 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |          2        0.02        0.02
          3 |          8        0.08        0.10
          4 |         20        0.20        0.30
          6 |        397        3.97        4.27
          7 |         13        0.13        4.40
          . |      9,560       95.60      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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