Frequencies for first 10,000 rows of contsub4 variable in nhamcsopd2000 dataset :

 controlled |
  substance |
   code for |
 medication |
         #4 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         15        0.15        0.15
          3 |         10        0.10        0.25
          4 |         55        0.55        0.80
          5 |          4        0.04        0.84
          6 |      1,264       12.64       13.48
          7 |         45        0.45       13.93
          . |      8,607       86.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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