Frequencies for first 10,000 rows of rx3v2c4 variable in nhamcsopd2006 dataset :

        for rx3, level 2 of multum drug |
                            category #4 |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
            CNS: Anti-Parkinson agents  |         17        0.17        0.17
                                      . |      9,983       99.83      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

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