Frequencies for first 10,000 rows of ld_chor variable in natlterr2011 dataset :

Chorioamnio |
  nitis RFP |
613=f_ld_ch |
     orio R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      2,536       25.36       25.36
          N |      6,360       63.60       88.96
          U |      1,092       10.92       99.88
          Y |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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