Frequencies for first 10,000 rows of pre4000 variable in natl1989 dataset :

   Previous |
     infant |
4000+ grams |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         51        0.51        0.51
          2 |      9,746       97.46       97.97
          9 |        203        2.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016