Frequencies for first 10,000 rows of rechal variable in drug2006q4 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,179       91.79       91.79
          D |        626        6.26       98.05
          N |         27        0.27       98.32
          U |        139        1.39       99.71
          Y |         29        0.29      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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