Frequencies for first 10,000 rows of dgestat variable in natl1983 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          4        0.04        0.04
         18 |          4        0.04        0.08
         19 |          2        0.02        0.10
         20 |          5        0.05        0.15
         21 |          1        0.01        0.16
         22 |          6        0.06        0.22
         23 |         14        0.14        0.36
         24 |          9        0.09        0.45
         25 |         21        0.21        0.66
         26 |         10        0.10        0.76
         27 |         29        0.29        1.05
         28 |         26        0.26        1.31
         29 |         37        0.37        1.68
         30 |         33        0.33        2.01
         31 |         52        0.52        2.53
         32 |         73        0.73        3.26
         33 |         90        0.90        4.16
         34 |        161        1.61        5.77
         35 |        261        2.61        8.38
         36 |        356        3.56       11.94
         37 |        560        5.60       17.54
         38 |      1,179       11.79       29.33
         39 |      1,795       17.95       47.28
         40 |      2,078       20.78       68.06
         41 |      1,449       14.49       82.55
         42 |        698        6.98       89.53
         43 |        306        3.06       92.59
         44 |        226        2.26       94.85
         45 |        147        1.47       96.32
         46 |         70        0.70       97.02
         47 |         32        0.32       97.34
         48 |         24        0.24       97.58
         49 |         14        0.14       97.72
         50 |          7        0.07       97.79
         51 |         11        0.11       97.90
         52 |          9        0.09       97.99
         99 |        201        2.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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