Frequencies for first 10,000 rows of hydra variable in natl1995 dataset :

Hydramnios/ |
Oligohydram |
       nios |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         48        0.48        0.48
          2 |      9,909       99.09       99.57
          9 |         43        0.43      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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