Frequencies for first 10,000 rows of tocol variable in natl1992 dataset :

  Tocolysis |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         76        0.76        0.76
          2 |      9,913       99.13       99.89
          9 |         11        0.11      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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