Frequencies for first 10,000 rows of phyper variable in natl1991 dataset :

Hypertensio |
        n - |
  pregnancy |
 associated |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        289        2.89        2.89
          2 |      9,704       97.04       99.93
          9 |          7        0.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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