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

Chorioamnio |
  nitis RFP |
613=f_ld_ch |
     orio R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,449       24.49       24.49
          N |      7,533       75.33       99.82
          U |          2        0.02       99.84
          Y |         16        0.16      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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