Frequencies for first 10,000 rows of rechal variable in drug2009q2 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,878       98.78       98.78
          D |        106        1.06       99.84
          N |          4        0.04       99.88
          U |          2        0.02       99.90
          Y |         10        0.10      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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