Frequencies for first 10,000 rows of nprevis variable in natl1979 dataset :

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        116        1.16        1.16
          1 |        138        1.38        2.54
          2 |        189        1.89        4.43
          3 |        245        2.45        6.88
          4 |        330        3.30       10.18
          5 |        462        4.62       14.80
          6 |        561        5.61       20.41
          7 |        538        5.38       25.79
          8 |        673        6.73       32.52
          9 |        735        7.35       39.87
         10 |      1,286       12.86       52.73
         11 |        799        7.99       60.72
         12 |      1,572       15.72       76.44
         13 |        665        6.65       83.09
         14 |        668        6.68       89.77
         15 |        482        4.82       94.59
         16 |        165        1.65       96.24
         17 |         70        0.70       96.94
         18 |         72        0.72       97.66
         19 |         20        0.20       97.86
         20 |         69        0.69       98.55
         21 |          8        0.08       98.63
         22 |          6        0.06       98.69
         23 |          1        0.01       98.70
         25 |          5        0.05       98.75
         26 |          1        0.01       98.76
         28 |          3        0.03       98.79
         29 |          1        0.01       98.80
         30 |         11        0.11       98.91
         32 |          3        0.03       98.94
         33 |          1        0.01       98.95
         34 |          1        0.01       98.96
         99 |        104        1.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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