Frequencies for first 10,000 rows of contsub4 variable in nhamcsopd1994 dataset :

 controlled |
  substance |
   code for |
 medication |
         #4 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |          7        0.07        0.07
          3 |          6        0.06        0.13
          4 |         28        0.28        0.41
          5 |          3        0.03        0.44
          6 |        740        7.40        7.84
          7 |         55        0.55        8.39
          . |      9,161       91.61      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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