Frequencies for first 10,000 rows of dgestat variable in natl1980 dataset :

  Gestation |      Freq.     Percent        Cum.
------------+-----------------------------------
         17 |          2        0.02        0.02
         18 |          1        0.01        0.03
         19 |          3        0.03        0.06
         20 |          1        0.01        0.07
         21 |          2        0.02        0.09
         22 |          2        0.02        0.11
         23 |          4        0.04        0.15
         24 |          3        0.03        0.18
         25 |          2        0.02        0.20
         26 |         17        0.17        0.37
         27 |         14        0.14        0.51
         28 |         16        0.16        0.67
         29 |         24        0.24        0.91
         30 |         27        0.27        1.18
         31 |         44        0.44        1.62
         32 |         55        0.55        2.17
         33 |         60        0.60        2.77
         34 |        121        1.21        3.98
         35 |        171        1.71        5.69
         36 |        283        2.83        8.52
         37 |        452        4.52       13.04
         38 |        950        9.50       22.54
         39 |      1,470       14.70       37.24
         40 |      1,766       17.66       54.90
         41 |      1,183       11.83       66.73
         42 |        676        6.76       73.49
         43 |        313        3.13       76.62
         44 |        187        1.87       78.49
         45 |         98        0.98       79.47
         46 |         49        0.49       79.96
         47 |         29        0.29       80.25
         48 |         17        0.17       80.42
         49 |         15        0.15       80.57
         50 |          7        0.07       80.64
         51 |         11        0.11       80.75
         52 |          3        0.03       80.78
         99 |      1,922       19.22      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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