Frequencies for first 10,000 rows of monprec variable in natl1985 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         79        0.79        0.79
          0 |        158        1.58        2.37
          1 |      1,089       10.89       13.26
          2 |      3,842       38.42       51.68
          3 |      2,304       23.04       74.72
          4 |      1,077       10.77       85.49
          5 |        610        6.10       91.59
          6 |        350        3.50       95.09
          7 |        285        2.85       97.94
          8 |        138        1.38       99.32
          9 |         68        0.68      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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