Frequencies for first 10,000 rows of f_on_rupture variable in natl2006 dataset :

  Premature |
 Rupture of |
        the |
  Membranes |
 (on_ruptr) |
          R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,991       99.91       99.91
          1 |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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