Frequencies for first 10,000 rows of rf_ppterm variable in natlterr2009 dataset :

   Previous |
    Preterm |
  Birth RFP |
587=f_rf_pp |
        b R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,449       24.49       24.49
          N |      7,431       74.31       98.80
          U |          2        0.02       98.82
          Y |        118        1.18      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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