Frequencies for first 10,000 rows of dechal variable in drug2010q2 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,893       98.93       98.93
          D |         63        0.63       99.56
          N |         10        0.10       99.66
          U |         12        0.12       99.78
          Y |         22        0.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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