Frequencies for first 10,000 rows of dechal variable in drug2010q4 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,947       99.47       99.47
          D |         35        0.35       99.82
          N |          7        0.07       99.89
          Y |         11        0.11      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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