Frequencies for first 10,000 rows of urf_preterm variable in natlterr2005 dataset :

   Previous |
 Preterm or |
  Small for |
Gestation U |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         10        0.10        0.10
          2 |      4,458       44.58       44.68
          9 |      1,787       17.87       62.55
          . |      3,745       37.45      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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