Frequencies for first 10,000 rows of comstat2 variable in nhamcsed2011 dataset :

Composition status |
          code for |
     medication #2 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      4,384       43.84       43.84
  Combination drug |        755        7.55       51.39
      Undetermined |         56        0.56       51.95
                 . |      4,805       48.05      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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