Frequencies for first 10,000 rows of comstat3 variable in nhamcsopd2005 dataset :

composition status |
   code for med #3 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
single entity drug |      2,343       23.43       23.43
  combination drug |        309        3.09       26.52
      undetermined |         50        0.50       27.02
                 . |      7,298       72.98      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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