Frequencies for first 10,000 rows of dechal variable in drug2011q2 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,973       99.73       99.73
          D |         20        0.20       99.93
          N |          4        0.04       99.97
          Y |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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