Frequencies for first 10,000 rows of dechal variable in drug2010q3 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,955       99.55       99.55
          D |         30        0.30       99.85
          N |          4        0.04       99.89
          U |          2        0.02       99.91
          Y |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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