Frequencies for first 10,000 rows of clingest variable in natlterr1996 dataset :

   Clinical |
Estimate of |
  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         18 |          1        0.01        0.01
         21 |          3        0.03        0.04
         22 |          2        0.02        0.06
         23 |          4        0.04        0.10
         24 |          2        0.02        0.12
         25 |         11        0.11        0.23
         26 |          9        0.09        0.32
         27 |         11        0.11        0.43
         28 |         16        0.16        0.59
         29 |         18        0.18        0.77
         30 |         23        0.23        1.00
         31 |         22        0.22        1.22
         32 |         45        0.45        1.67
         33 |         58        0.58        2.25
         34 |        108        1.08        3.33
         35 |        201        2.01        5.34
         36 |        358        3.58        8.92
         37 |        843        8.43       17.35
         38 |      1,801       18.01       35.36
         39 |      2,330       23.30       58.66
         40 |      2,992       29.92       88.58
         41 |        883        8.83       97.41
         42 |        233        2.33       99.74
         43 |         15        0.15       99.89
         99 |         11        0.11      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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