Frequencies for first 10,000 rows of ewarn variable in namcs2007 dataset :

   if yes, are |
there warnings |
       of drug |
interact/contr |
         aind? |      Freq.     Percent        Cum.
---------------+-----------------------------------
         blank |        210        2.10        2.10
       unknown |        431        4.31        6.41
not applicable |      6,669       66.69       73.10
           yes |      2,206       22.06       95.16
            no |        484        4.84      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

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