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

Hypertensio |
        n - |
  pregnancy |
 associated |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        314        3.14        3.14
          2 |      9,638       96.38       99.52
          9 |         48        0.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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