Frequencies for first 10,000 rows of rf_phyp variable in natlterr2012 dataset :

Prepregnanc |
          y |
Hypertensio |
      n RFP |
584=f_rf_ph |
     yper R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,163       11.63       11.63
          N |      8,390       83.90       95.53
          U |        335        3.35       98.88
          Y |        112        1.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 5 May 2016