Frequencies for first 10,000 rows of contsub2 variable in nhamcsopd1999 dataset :

 controlled |
  substance |
   code for |
 medication |
         #2 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |        104        1.04        1.04
          3 |         38        0.38        1.42
          4 |        230        2.30        3.72
          5 |          7        0.07        3.79
          6 |      3,195       31.95       35.74
          7 |        133        1.33       37.07
          . |      6,293       62.93      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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