Frequencies for first 10,000 rows of rx6v1c3 variable in nhamcsopd2006 dataset :

   for rx6, level 1 of multum |
             drug category #3 |      Freq.     Percent        Cum.
------------------------------+-----------------------------------
Central nervous system agents |          3        0.03        0.03
         Miscellaneous agents |          3        0.03        0.06
                            . |      9,994       99.94      100.00
------------------------------+-----------------------------------
                        Total |     10,000      100.00

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