Frequencies for first 10,000 rows of comstat4 variable in nhamcsopd2005 dataset :

composition status |
   code for med #4 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
single entity drug |      1,535       15.35       15.35
  combination drug |        169        1.69       17.04
      undetermined |         28        0.28       17.32
                 . |      8,268       82.68      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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