Frequencies for first 10,000 rows of nprevis variable in natl1981 dataset :

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        142        1.42        1.42
          1 |        200        2.00        3.42
          2 |        181        1.81        5.23
          3 |        228        2.28        7.51
          4 |        290        2.90       10.41
          5 |        333        3.33       13.74
          6 |        483        4.83       18.57
          7 |        521        5.21       23.78
          8 |        636        6.36       30.14
          9 |        629        6.29       36.43
         10 |      1,231       12.31       48.74
         11 |        719        7.19       55.93
         12 |      1,720       17.20       73.13
         13 |        695        6.95       80.08
         14 |        796        7.96       88.04
         15 |        527        5.27       93.31
         16 |        226        2.26       95.57
         17 |         89        0.89       96.46
         18 |         79        0.79       97.25
         19 |         40        0.40       97.65
         20 |         81        0.81       98.46
         21 |         22        0.22       98.68
         22 |         11        0.11       98.79
         23 |          7        0.07       98.86
         24 |          4        0.04       98.90
         25 |         14        0.14       99.04
         26 |          2        0.02       99.06
         27 |          1        0.01       99.07
         28 |          2        0.02       99.09
         30 |          2        0.02       99.11
         35 |          1        0.01       99.12
         45 |          1        0.01       99.13
         99 |         87        0.87      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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