Frequencies for first 10,000 rows of contsub1 variable in nhamcsopd1994 dataset :

 controlled |
  substance |
   code for |
 medication |
         #1 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |        105        1.05        1.05
          3 |         62        0.62        1.67
          4 |        124        1.24        2.91
          5 |         10        0.10        3.01
          6 |      5,375       53.75       56.76
          7 |        418        4.18       60.94
          . |      3,906       39.06      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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