Frequencies for first 10,000 rows of op_tocol variable in natlterr2007 dataset :

  Tocolysis |
        RFP |
602=f_ob_to |
       co R |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      6,163       61.63       61.63
          N |      3,736       37.36       98.99
          U |          1        0.01       99.00
          Y |        100        1.00      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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