Frequencies for first 10,000 rows of dgestat variable in natl1985 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          3        0.03        0.03
         18 |          2        0.02        0.05
         19 |          4        0.04        0.09
         20 |          5        0.05        0.14
         21 |          8        0.08        0.22
         22 |          8        0.08        0.30
         23 |         10        0.10        0.40
         24 |         12        0.12        0.52
         25 |         18        0.18        0.70
         26 |         15        0.15        0.85
         27 |         14        0.14        0.99
         28 |         22        0.22        1.21
         29 |         31        0.31        1.52
         30 |         39        0.39        1.91
         31 |         59        0.59        2.50
         32 |         80        0.80        3.30
         33 |        119        1.19        4.49
         34 |        171        1.71        6.20
         35 |        236        2.36        8.56
         36 |        320        3.20       11.76
         37 |        613        6.13       17.89
         38 |      1,130       11.30       29.19
         39 |      1,906       19.06       48.25
         40 |      2,034       20.34       68.59
         41 |      1,405       14.05       82.64
         42 |        751        7.51       90.15
         43 |        304        3.04       93.19
         44 |        181        1.81       95.00
         45 |        104        1.04       96.04
         46 |         53        0.53       96.57
         47 |         35        0.35       96.92
         48 |         25        0.25       97.17
         49 |         14        0.14       97.31
         50 |          8        0.08       97.39
         51 |         13        0.13       97.52
         52 |          4        0.04       97.56
         99 |        244        2.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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