Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1993 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         47        0.47        0.47
          3 |         37        0.37        0.84
          4 |        151        1.51        2.35
          5 |         11        0.11        2.46
          6 |      2,750       27.50       29.96
          7 |        202        2.02       31.98
          . |      6,802       68.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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