Frequencies for first 10,000 rows of rechal variable in drug2010q2 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,894       98.94       98.94
          D |         89        0.89       99.83
          N |          2        0.02       99.85
          U |         12        0.12       99.97
          Y |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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