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

Hypertensio |
        n - |
  pregnancy |
 associated |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        310        3.10        3.10
          2 |      9,647       96.47       99.57
          9 |         43        0.43      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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