Frequencies for first 10,000 rows of rx4cat4 variable in nhamcsopd2006 dataset :

     for rx4, multum drug category #4 - |
                               detailed |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
CNS: Anti-Parkinson agents: anticholine |          4        0.04        0.04
                                      . |      9,996       99.96      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

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