Frequencies for first 10,000 rows of f_urf_phyper variable in natl2009 dataset :

  Pregnancy |
 Associated |
Hypertensio |
          n |
(urf_phyper |
      ) U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         40        0.40        0.40
          1 |      9,960       99.60      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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