Frequencies for first 10,000 rows of dechal variable in drug2012q4 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,845       98.45       98.45
          D |         97        0.97       99.42
          N |         11        0.11       99.53
          U |         23        0.23       99.76
          Y |         24        0.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 19 Apr 2017