Frequencies for first 10,000 rows of rechal variable in drug2009q4 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,679       96.79       96.79
          D |        287        2.87       99.66
          N |          6        0.06       99.72
          U |         25        0.25       99.97
          Y |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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