Frequencies for first 10,000 rows of rechal variable in drug2006q1 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,169       91.69       91.69
          D |        634        6.34       98.03
          N |          8        0.08       98.11
          U |        179        1.79       99.90
          Y |         10        0.10      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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