Frequencies for first 10,000 rows of rf_ppterm variable in natlterr2010 dataset :

   Previous |
    Preterm |
  Birth RFP |
587=f_rf_pp |
        b R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      4,656       46.56       46.56
          N |      4,503       45.03       91.59
          U |        767        7.67       99.26
          Y |         74        0.74      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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