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

   Clinical |
Estimate of |
  Gestation |
  Used Flag |
        U;R |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,941       19.41       19.41
          . |      8,059       80.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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