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

   Abruptio |
   placenta |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         54        0.54        0.54
          2 |      9,647       96.47       97.01
          9 |        299        2.99      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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