Frequencies for first 10,000 rows of comstat3 variable in nhamcsed2013 dataset :

Composition status |
          code for |
     medication #3 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      2,844       28.44       28.44
  Combination drug |        424        4.24       32.68
      Undetermined |         35        0.35       33.03
                 . |      6,697       66.97      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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