Frequencies for first 10,000 rows of contsub6 variable in nhamcsopd1995 dataset :

 controlled |
  substance |
   code for |
 medication |
         #6 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |          7        0.07        0.07
          3 |          5        0.05        0.12
          4 |         14        0.14        0.26
          6 |        345        3.45        3.71
          7 |         10        0.10        3.81
          . |      9,619       96.19      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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