Frequencies for first 10,000 rows of rupture variable in linkco1991us_num dataset :

  Premature |
 rupture of |
   membrane |
(>12 hours) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,218       12.18       12.18
          2 |      8,575       85.75       97.93
          9 |        207        2.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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