Frequencies for first 10,000 rows of comstat2 variable in nhamcsed2005 dataset :

composition status |
              code |      Freq.     Percent        Cum.
-------------------+-----------------------------------
single entity drug |      4,200       42.00       42.00
  combination drug |        762        7.62       49.62
      undetermined |        107        1.07       50.69
                 . |      4,931       49.31      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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