Frequencies for first 10,000 rows of dechal variable in drug2013q4 dataset :

Dechallenge |
      code, |
 indicating |
if reaction |
abated when |
       drug |
therapy was |
    stopped |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,867       98.67       98.67
          D |         78        0.78       99.45
          N |         21        0.21       99.66
          U |         11        0.11       99.77
          Y |         23        0.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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