Frequencies for first 10,000 rows of gestwk variable in nhamcsopd2005 dataset :

       week of |
     gestation |      Freq.     Percent        Cum.
---------------+-----------------------------------
             3 |          1        0.01        0.01
             4 |          1        0.01        0.02
             5 |          4        0.04        0.06
             6 |          4        0.04        0.10
             7 |          5        0.05        0.15
             8 |         11        0.11        0.26
             9 |         12        0.12        0.38
            10 |         12        0.12        0.50
            11 |         18        0.18        0.68
            12 |         19        0.19        0.87
            13 |         10        0.10        0.97
            14 |         15        0.15        1.12
            15 |          4        0.04        1.16
            16 |         11        0.11        1.27
            17 |         12        0.12        1.39
            18 |         15        0.15        1.54
            19 |         21        0.21        1.75
            20 |         23        0.23        1.98
            21 |         17        0.17        2.15
            22 |         14        0.14        2.29
            23 |         15        0.15        2.44
            24 |         18        0.18        2.62
            25 |         18        0.18        2.80
            26 |         20        0.20        3.00
            27 |         20        0.20        3.20
            28 |         23        0.23        3.43
            29 |         22        0.22        3.65
            30 |         29        0.29        3.94
            31 |         27        0.27        4.21
            32 |         25        0.25        4.46
            33 |         28        0.28        4.74
            34 |         40        0.40        5.14
            35 |         27        0.27        5.41
            36 |         32        0.32        5.73
            37 |         54        0.54        6.27
            38 |         45        0.45        6.72
            39 |         18        0.18        6.90
            40 |         13        0.13        7.03
            41 |          3        0.03        7.06
            42 |          1        0.01        7.07
            44 |          6        0.06        7.13
not applicable |      8,542       85.42       92.55
         blank |        745        7.45      100.00
---------------+-----------------------------------
         Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016