Frequencies for first 10,000 rows of dechal variable in drug2009q2 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,873       98.73       98.73
          D |         57        0.57       99.30
          N |         14        0.14       99.44
          U |          2        0.02       99.46
          Y |         54        0.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 18 Dec 2015