Frequencies for first 10,000 rows of rupture variable in natl1991 dataset :

  Premature |
 rupture of |
   membrane |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        180        1.80        1.80
          2 |      9,790       97.90       99.70
          9 |         30        0.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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