Frequencies for first 10,000 rows of clingest variable in natl1999 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         18 |          2        0.02        0.02
         19 |          2        0.02        0.04
         20 |          5        0.05        0.09
         21 |          6        0.06        0.15
         22 |          6        0.06        0.21
         23 |          6        0.06        0.27
         24 |         17        0.17        0.44
         25 |         14        0.14        0.58
         26 |         17        0.17        0.75
         27 |         15        0.15        0.90
         28 |         28        0.28        1.18
         29 |         24        0.24        1.42
         30 |         28        0.28        1.70
         31 |         42        0.42        2.12
         32 |         50        0.50        2.62
         33 |         73        0.73        3.35
         34 |        122        1.22        4.57
         35 |        235        2.35        6.92
         36 |        436        4.36       11.28
         37 |        795        7.95       19.23
         38 |      1,634       16.34       35.57
         39 |      2,555       25.55       61.12
         40 |      2,953       29.53       90.65
         41 |        806        8.06       98.71
         42 |        106        1.06       99.77
         43 |          6        0.06       99.83
         44 |          1        0.01       99.84
         99 |         16        0.16      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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