Frequencies for first 10,000 rows of advdrug variable in nhamcsed2001 dataset :

 is visit related to an adverse drug |
                              event? |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
                               Blank |        807        8.07        8.07
                                 Yes |        427        4.27       12.34
                                  No |      2,245       22.45       34.79
                             Unknown |        211        2.11       36.90
Not applicable (not an injury visit) |      6,310       63.10      100.00
-------------------------------------+-----------------------------------
                               Total |     10,000      100.00

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