Frequencies for first 10,000 rows of comstat4 variable in nhamcsed2012 dataset :

Composition status |
          code for |
     medication #4 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      1,533       15.33       15.33
  Combination drug |        247        2.47       17.80
      Undetermined |         20        0.20       18.00
                 . |      8,200       82.00      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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