Frequencies for first 10,000 rows of ewarne variable in nhamcsed2007 dataset :

   if yes, are |
there warnings |
       of drug |
 interactions? |      Freq.     Percent        Cum.
---------------+-----------------------------------
         blank |        103        1.03        1.03
       unknown |        321        3.21        4.24
not applicable |      4,807       48.07       52.31
           yes |      3,259       32.59       84.90
            no |      1,510       15.10      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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