Frequencies for first 10,000 rows of rechal variable in drug2004q3 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      8,138       81.38       81.38
          D |      1,670       16.70       98.08
          N |         21        0.21       98.29
          U |        129        1.29       99.58
          Y |         42        0.42      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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