Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1995 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         55        0.55        0.55
          3 |         38        0.38        0.93
          4 |        158        1.58        2.51
          5 |          8        0.08        2.59
          6 |      3,160       31.60       34.19
          7 |        132        1.32       35.51
          . |      6,449       64.49      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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