Frequencies for first 10,000 rows of rechal variable in drug2008q1 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,826       98.26       98.26
          D |        146        1.46       99.72
          N |          2        0.02       99.74
          U |         13        0.13       99.87
          Y |         13        0.13      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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