Frequencies for first 10,000 rows of comstat4 variable in nhamcsopd2011 dataset :

Composition status |
          code for |
     Medication #4 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      2,525       25.25       25.25
  Combination drug |        186        1.86       27.11
      Undetermined |         33        0.33       27.44
                 . |      7,256       72.56      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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