Frequencies for first 10,000 rows of comstat2 variable in nhamcsed2013 dataset :

Composition status |
          code for |
     medication #2 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      4,597       45.97       45.97
  Combination drug |        679        6.79       52.76
      Undetermined |         53        0.53       53.29
                 . |      4,671       46.71      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016