Frequencies for first 10,000 rows of f_urf_phyper variable in natl2006 dataset :

  Pregnancy |
 Associated |
Hypertensio |
          n |
(urf_phyper |
        ) U |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |          4        0.04        0.04
          1 |      9,996       99.96      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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