Frequencies for first 10,000 rows of contsub4 variable in nhamcsopd1996 dataset :

 controlled |
  substance |
   code for |
 medication |
         #4 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |         15        0.15        0.15
          3 |         14        0.14        0.29
          4 |         43        0.43        0.72
          5 |          3        0.03        0.75
          6 |      1,173       11.73       12.48
          7 |         43        0.43       12.91
          . |      8,709       87.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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