Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1996 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         66        0.66        0.66
          3 |         38        0.38        1.04
          4 |        241        2.41        3.45
          5 |         10        0.10        3.55
          6 |      3,200       32.00       35.55
          7 |        165        1.65       37.20
          . |      6,280       62.80      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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