Frequencies for first 10,000 rows of nprevis variable in natl1977 dataset :

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        124        1.24        1.24
          1 |        168        1.68        2.92
          2 |        195        1.95        4.87
          3 |        251        2.51        7.38
          4 |        348        3.48       10.86
          5 |        439        4.39       15.25
          6 |        511        5.11       20.36
          7 |        516        5.16       25.52
          8 |        788        7.88       33.40
          9 |        708        7.08       40.48
         10 |      1,270       12.70       53.18
         11 |        756        7.56       60.74
         12 |      1,515       15.15       75.89
         13 |        798        7.98       83.87
         14 |        551        5.51       89.38
         15 |        467        4.67       94.05
         16 |        157        1.57       95.62
         17 |         50        0.50       96.12
         18 |         75        0.75       96.87
         19 |         19        0.19       97.06
         20 |         93        0.93       97.99
         21 |         19        0.19       98.18
         22 |         12        0.12       98.30
         23 |          4        0.04       98.34
         24 |          5        0.05       98.39
         25 |          8        0.08       98.47
         26 |          3        0.03       98.50
         28 |          2        0.02       98.52
         29 |          1        0.01       98.53
         30 |          6        0.06       98.59
         31 |          1        0.01       98.60
         35 |          2        0.02       98.62
         99 |        138        1.38      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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