Frequencies for first 10,000 rows of advdrug variable in nhamcsed2002 dataset :

 is visit related to an adverse drug |
                              event? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                               Blank |        985        9.85        9.85
                                 Yes |        407        4.07       13.92
                                  No |      1,906       19.06       32.98
                             Unknown |        207        2.07       35.05
Not applicable (not an injury visit) |      6,495       64.95      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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