Frequencies for first 10,000 rows of contsub1 variable in nhamcsopd1993 dataset :

 controlled |
  substance |
   code for |
 medication |
         #1 |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |        117        1.17        1.17
          3 |         78        0.78        1.95
          4 |        156        1.56        3.51
          5 |          6        0.06        3.57
          6 |      4,849       48.49       52.06
          7 |        438        4.38       56.44
          . |      4,356       43.56      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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