Frequencies for first 10,000 rows of rechal variable in drug2008q3 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,783       97.83       97.83
          D |        197        1.97       99.80
          N |          3        0.03       99.83
          U |         17        0.17      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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