Frequencies for first 10,000 rows of dechal variable in drug2009q4 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,688       96.88       96.88
          D |        213        2.13       99.01
          N |         27        0.27       99.28
          U |         25        0.25       99.53
          Y |         47        0.47      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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