Frequencies for first 10,000 rows of hydra variable in natlterr1998 dataset :

Hydramnios/ |
Oligohydram |
       nios |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         70        0.70        0.70
          2 |      9,928       99.28       99.98
          9 |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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