Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd2000 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         86        0.86        0.86
          3 |         50        0.50        1.36
          4 |        186        1.86        3.22
          5 |          8        0.08        3.30
          6 |      3,147       31.47       34.77
          7 |        152        1.52       36.29
          . |      6,371       63.71      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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