Frequencies for first 10,000 rows of rechal variable in drug2006q2 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,701       97.01       97.01
          D |        268        2.68       99.69
          N |          1        0.01       99.70
          U |         18        0.18       99.88
          Y |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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