Frequencies for first 10,000 rows of rf_ppterm variable in natlterr2008 dataset :

   Previous |
    Preterm |
  Birth RFP |
587=f_rf_pp |
        b R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      6,061       60.61       60.61
          N |      3,893       38.93       99.54
          Y |         46        0.46      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 May 2016