Frequencies for first 10,000 rows of nprevis variable in natl1990 dataset :

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        189        1.89        1.89
          1 |         62        0.62        2.51
          2 |        106        1.06        3.57
          3 |        151        1.51        5.08
          4 |        197        1.97        7.05
          5 |        276        2.76        9.81
          6 |        406        4.06       13.87
          7 |        430        4.30       18.17
          8 |        641        6.41       24.58
          9 |        611        6.11       30.69
         10 |      1,443       14.43       45.12
         11 |        752        7.52       52.64
         12 |      1,798       17.98       70.62
         13 |        621        6.21       76.83
         14 |        674        6.74       83.57
         15 |        618        6.18       89.75
         16 |        339        3.39       93.14
         17 |        113        1.13       94.27
         18 |        112        1.12       95.39
         19 |         46        0.46       95.85
         20 |        158        1.58       97.43
         21 |         21        0.21       97.64
         22 |         15        0.15       97.79
         23 |         13        0.13       97.92
         24 |         12        0.12       98.04
         25 |         31        0.31       98.35
         26 |          5        0.05       98.40
         27 |          9        0.09       98.49
         28 |          1        0.01       98.50
         29 |          4        0.04       98.54
         30 |         24        0.24       98.78
         31 |          1        0.01       98.79
         32 |          2        0.02       98.81
         35 |          2        0.02       98.83
         38 |          1        0.01       98.84
         39 |          1        0.01       98.85
         40 |          1        0.01       98.86
         41 |          1        0.01       98.87
         45 |          2        0.02       98.89
         49 |          1        0.01       98.90
         99 |        110        1.10      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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