Frequencies for first 10,000 rows of clingest variable in natlterr1999 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         20 |          2        0.02        0.02
         21 |          2        0.02        0.04
         22 |          9        0.09        0.13
         23 |          3        0.03        0.16
         24 |          9        0.09        0.25
         25 |          5        0.05        0.30
         26 |         10        0.10        0.40
         27 |         18        0.18        0.58
         28 |         23        0.23        0.81
         29 |         15        0.15        0.96
         30 |         20        0.20        1.16
         31 |         36        0.36        1.52
         32 |         49        0.49        2.01
         33 |         75        0.75        2.76
         34 |        113        1.13        3.89
         35 |        177        1.77        5.66
         36 |        491        4.91       10.57
         37 |      1,041       10.41       20.98
         38 |      2,201       22.01       42.99
         39 |      2,384       23.84       66.83
         40 |      2,623       26.23       93.06
         41 |        541        5.41       98.47
         42 |        136        1.36       99.83
         43 |          9        0.09       99.92
         99 |          8        0.08      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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