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

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         65        0.65        0.65
          0 |        124        1.24        1.89
          1 |        759        7.59        9.48
          2 |      3,686       36.86       46.34
          3 |      2,384       23.84       70.18
          4 |      1,256       12.56       82.74
          5 |        727        7.27       90.01
          6 |        458        4.58       94.59
          7 |        287        2.87       97.46
          8 |        164        1.64       99.10
          9 |         90        0.90      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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