Frequencies for first 10,000 rows of rf_ppterm variable in natlterr2006 dataset :

   Previous |
    Preterm |
  Birth RFP |
587=f_rf_pp |
        b R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      6,275       62.75       62.75
          N |      3,675       36.75       99.50
          Y |         50        0.50      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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