Frequencies for first 10,000 rows of comstat4 variable in nhamcsed2011 dataset :

Composition status |
          code for |
     medication #4 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      1,392       13.92       13.92
  Combination drug |        237        2.37       16.29
      Undetermined |         17        0.17       16.46
                 . |      8,354       83.54      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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