Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1997 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         48        0.48        0.48
          3 |         38        0.38        0.86
          4 |        190        1.90        2.76
          5 |         10        0.10        2.86
          6 |      2,933       29.33       32.19
          7 |        112        1.12       33.31
          . |      6,669       66.69      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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