Frequencies for first 10,000 rows of contsub3 variable in nhamcsopd1996 dataset :

 controlled |
  substance |
   code for |
 medication |
         #3 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         30        0.30        0.30
          3 |         24        0.24        0.54
          4 |         91        0.91        1.45
          5 |          5        0.05        1.50
          6 |      1,997       19.97       21.47
          7 |         87        0.87       22.34
          . |      7,766       77.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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