Frequencies for first 10,000 rows of monprec variable in natl1980 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         83        0.83        0.83
          0 |        125        1.25        2.08
          1 |      1,186       11.86       13.94
          2 |      3,559       35.59       49.53
          3 |      2,182       21.82       71.35
          4 |      1,100       11.00       82.35
          5 |        677        6.77       89.12
          6 |        455        4.55       93.67
          7 |        336        3.36       97.03
          8 |        199        1.99       99.02
          9 |         98        0.98      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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