Frequencies for first 10,000 rows of contsub4 variable in nhamcsopd1995 dataset :

 controlled |
  substance |
   code for |
 medication |
         #4 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         14        0.14        0.14
          3 |         18        0.18        0.32
          4 |         38        0.38        0.70
          5 |          3        0.03        0.73
          6 |        981        9.81       10.54
          7 |         38        0.38       10.92
          . |      8,908       89.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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