Frequencies for first 10,000 rows of rx1v1c4 variable in nhamcsopd2006 dataset :

   for rx1, level 1 of multum |
             drug category #4 |      Freq.     Percent        Cum.
------------------------------+-----------------------------------
Central nervous system agents |         19        0.19        0.19
                            . |      9,981       99.81      100.00
------------------------------+-----------------------------------
                        Total |     10,000      100.00

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