Frequencies for first 10,000 rows of contsub4 variable in nhamcsopd1993 dataset :

 controlled |
  substance |
   code for |
 medication |
         #4 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         22        0.22        0.22
          3 |         11        0.11        0.33
          4 |         38        0.38        0.71
          5 |          3        0.03        0.74
          6 |        803        8.03        8.77
          7 |         81        0.81        9.58
          . |      9,042       90.42      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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