Frequencies for first 10,000 rows of abruptio variable in natl1990 dataset :

   Abruptio |
   placenta |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         54        0.54        0.54
          2 |      9,880       98.80       99.34
          9 |         66        0.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016