Frequencies for first 10,000 rows of comstat2 variable in nhamcsopd2005 dataset :

composition status |
   code for med #2 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
single entity drug |      3,484       34.84       34.84
  combination drug |        598        5.98       40.82
      undetermined |        117        1.17       41.99
                 . |      5,801       58.01      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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