Frequencies for first 10,000 rows of injury variable in nhamcsed2012 dataset :

       Is visit related to |
      injury, poisoning or |
 adverse effect of medical |
             treatment? -  |      Freq.     Percent        Cum.
---------------------------+-----------------------------------
                     Blank |         57        0.57        0.57
                   Unknown |        494        4.94        5.51
                        No |      6,013       60.13       65.64
                       Yes |      3,436       34.36      100.00
---------------------------+-----------------------------------
                     Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016