Frequencies for first 10,000 rows of phyper variable in natl2002 dataset :

Hypertensio |
        n - |
pregnancy-a |
  ssociated |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        297        2.97        2.97
          2 |      9,390       93.90       96.87
          9 |        313        3.13      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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