Frequencies for first 10,000 rows of ewarn variable in namcs2009 dataset :

   if yes, are |
there warnings |
       of drug |
interact/contr |
         aind? |      Freq.     Percent        Cum.
---------------+-----------------------------------
         blank |        128        1.28        1.28
       unknown |        232        2.32        3.60
not applicable |      4,888       48.88       52.48
           yes |      4,333       43.33       95.81
            no |        419        4.19      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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