Frequencies for first 10,000 rows of phyper variable in natl1999 dataset :

Hypertensio |
        n - |
  pregnancy |
 associated |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        531        5.31        5.31
          2 |      9,468       94.68       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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