Frequencies for first 10,000 rows of gestat10 variable in natl1988 dataset :

  Gestation |
  Recode 10 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |          6        0.06        0.06
          2 |        105        1.05        1.11
          3 |        149        1.49        2.60
          4 |        568        5.68        8.28
          5 |        353        3.53       11.81
          6 |      3,700       37.00       48.81
          7 |      2,025       20.25       69.06
          8 |      1,292       12.92       81.98
          9 |      1,480       14.80       96.78
         10 |        322        3.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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