Frequencies for first 10,000 rows of contsub5 variable in nhamcsopd1995 dataset :

 controlled |
  substance |
   code for |
 medication |
         #5 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |          3        0.03        0.03
          3 |          4        0.04        0.07
          4 |         31        0.31        0.38
          6 |        603        6.03        6.41
          7 |         23        0.23        6.64
          . |      9,336       93.36      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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