Frequencies for first 10,000 rows of rf_phyp variable in natlterr2011 dataset :

Prepregnanc |
          y |
Hypertensio |
      n RFP |
584=f_rf_ph |
     yper R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,536       25.36       25.36
          N |      6,289       62.89       88.25
          U |      1,074       10.74       98.99
          Y |        101        1.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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