Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1994 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         17        0.17        0.17
          3 |         38        0.38        0.55
          4 |        110        1.10        1.65
          5 |         13        0.13        1.78
          6 |      2,867       28.67       30.45
          7 |        215        2.15       32.60
          . |      6,740       67.40      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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