Frequencies for first 10,000 rows of rechal variable in drug2007q1 dataset :

Rechallenge |
      code, |
 indicating |
if reaction |
   recurred |
  when drug |
    therapy |
  restarted |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      9,580       95.80       95.80
          D |        364        3.64       99.44
          N |          8        0.08       99.52
          U |         41        0.41       99.93
          Y |          7        0.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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