Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1992 dataset :

 Controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         24        0.24        0.24
          3 |         28        0.28        0.52
          4 |         71        0.71        1.23
          5 |         17        0.17        1.40
          6 |      2,352       23.52       24.92
          7 |        186        1.86       26.78
          . |      7,322       73.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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