Frequencies for first 10,000 rows of rupture variable in natl2002 dataset :

  Premature |
 rupture of |
   membrane |
(>12 hours) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        364        3.64        3.64
          2 |      9,337       93.37       97.01
          9 |        299        2.99      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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