Frequencies for first 10,000 rows of rupture variable in natlterr2002 dataset :

  Premature |
 rupture of |
   membrane |
(>12 hours) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        148        1.48        1.48
          2 |      9,830       98.30       99.78
          8 |         14        0.14       99.92
          9 |          8        0.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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