Frequencies for first 10,000 rows of contsub3 variable in nhamcsopd1997 dataset :

 controlled |
  substance |
   code for |
 medication |
         #3 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         25        0.25        0.25
          3 |         15        0.15        0.40
          4 |         73        0.73        1.13
          5 |          2        0.02        1.15
          6 |      1,657       16.57       17.72
          7 |         65        0.65       18.37
          . |      8,163       81.63      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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