Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd2001 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         86        0.86        0.86
          3 |         44        0.44        1.30
          4 |        142        1.42        2.72
          5 |          4        0.04        2.76
          6 |      3,064       30.64       33.40
          7 |        195        1.95       35.35
          . |      6,465       64.65      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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