Frequencies for first 10,000 rows of gestat10 variable in natl1987 dataset :

  Gestation |
  Recode 10 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          6        0.06        0.06
          2 |         94        0.94        1.00
          3 |        155        1.55        2.55
          4 |        611        6.11        8.66
          5 |        381        3.81       12.47
          6 |      3,630       36.30       48.77
          7 |      2,005       20.05       68.82
          8 |      1,253       12.53       81.35
          9 |      1,570       15.70       97.05
         10 |        295        2.95      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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