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

  Premature |
 Rupture of |
   Membrane |
        RFP |
605=f_ol_ru |
    pture R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,449       24.49       24.49
          N |      7,455       74.55       99.04
          U |          2        0.02       99.06
          Y |         94        0.94      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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