Frequencies for first 10,000 rows of rechal variable in drug2007q3 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,565       95.65       95.65
          D |        375        3.75       99.40
          N |          6        0.06       99.46
          U |         38        0.38       99.84
          Y |         16        0.16      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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