Frequencies for first 10,000 rows of rupture variable in natl2001 dataset :

  Premature |
 rupture of |
   membrane |
(>12 hours) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        211        2.11        2.11
          2 |      9,787       97.87       99.98
          8 |          1        0.01       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015