Frequencies for first 10,000 rows of comstat1 variable in nhamcsopd2011 dataset :

Composition status |
          code for |
     Medication #1 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      5,734       57.34       57.34
  Combination drug |      1,098       10.98       68.32
      Undetermined |        130        1.30       69.62
                 . |      3,038       30.38      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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