Frequencies for first 10,000 rows of rechal variable in drug2011q4 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,949       99.49       99.49
          D |         43        0.43       99.92
          N |          5        0.05       99.97
          U |          2        0.02       99.99
          Y |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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