Frequencies for first 10,000 rows of comstat4 variable in namcs2012 dataset :

Composition status |
          code for |
      medication 4 |      Freq.     Percent        Cum.
-------------------+-----------------------------------
Single entity drug |      2,229       22.29       22.29
  Combination drug |        224        2.24       24.53
      Undetermined |         77        0.77       25.30
                 . |      7,470       74.70      100.00
-------------------+-----------------------------------
             Total |     10,000      100.00

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