Frequencies for first 10,000 rows of comstat4 variable in nhamcsed2013 dataset :

Composition status |
          code for |
     medication #4 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      1,735       17.35       17.35
  Combination drug |        249        2.49       19.84
      Undetermined |         19        0.19       20.03
                 . |      7,997       79.97      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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